Recently, I published the article, Hitting a Genealogy Home Run Using Your Double-Sided Two-Faced Chromosomes While Avoiding Imposters. The “Home Run” article explains why you want to use a chromosome browser, what you’re seeing and what it means to you.
This article, and the rest in the “Triangulation in Action” series introduces triangulation at FamilyTreeDNA, MyHeritage, 23andMe, GedMatch and DNAPainter, explaining how to use triangulation to confirm descent from a common ancestor. You may want to read the introductory article first.
This first section, “What is Triangulation” is a generic tutorial. If you don’t need the tutorial, skip to the “Triangulation at MyHeritage” section.
What is Triangulation?
Think of triangulation as a three-legged stool – a triangle. Triangulation requires three things:
- At least three (not closely related) people must match
- On the same reasonably sized segment of DNA and
- Descend from a common ancestor
Triangulation is the foundation of confirming descent from a common ancestor, and thereby assigning a specific segment to that ancestor. Without triangulation, you might just have a match to someone else by chance. You can confirm mathematical triangulation, numbers 1 and 2, above, without knowing the identity of the common ancestor.
Reasonably sized segments are generally considered to be 7cM or above on chromosomes 1-22 and 15cM or above for the X chromosome.
Triangulation means that all three, or more, people much match on a common segment. However, what you’re likely to see is that some people don’t match on the entire segment, meaning more or less than others as demonstrated in the following examples.
You can see that I match 5 different cousins who I know descend from my father’s side on chromosome 15 above. “I” am the grey background against which everyone else is being compared.
I triangulate with these matches in different ways, forming multiple triangulation groups that I’ve discussed individually, below.
Triangulation Group 1
Group 1 – On the left group of matches, above, I triangulate with the blue, red and orange person on the amount of DNA that is common between all of them, shown in the black box. This is triangulation group 1.
Triangulation Group 2
Group 2 – However, if you look just at the blue and orange triangulated matches bracketed in green, I triangulate on slightly more. This group excludes the red person because their beginning point is not the same, or even close. This is triangulation group 2.
Triangulation Group 3 and 4
Group 3 – In the right group of matches, there are two large triangulation groups. Triangulation group 3 includes the common portions of blue, red, teal and orange matches.
Group 4 – Triangulation group 4 is the skinny group at right and includes the common portion of the blue, teal and dark blue matches.
Triangulation Groups 5 and 6
Group 5 – There are also two more triangulation groups. The larger green bracketed group includes only the blue and teal people because their end locations are to the right of the end locations of the red and orange matches. This is triangulation group 5.
Group 6 – The smaller green bracketed group includes only the blue and teal person because their start locations are before the dark blue person. This is triangulation group 6.
There’s actually one more triangulation group. Can you see it?
Triangulation Group 7
Group 7 – The tan group includes the red, teal and orange matches but only the areas where they all overlap. This excludes the top blue match because their start location is different. Triangulation group 7 only extends to the end of the red and orange matches, because those are the same locations, while the teal match extends further to the right. That extension is excluded, of course.
Matches with only slight start and end differences are probably descended from the same ancestor, but we can’t say that for sure (at this point) so we only include actual mathematically matching segments in a triangulation group.
You can see that triangulation groups often overlap because group members share more or less DNA with each other. Normally we don’t bother to number the groups – we just look at the alignment. I numbered them for illustration purposes.
Shared or In-Common-With Matching
Triangulation is not the same thing as a 3-way shared “in-common-with” match. You may share DNA with those two people, but on entirely different segments from entirely different ancestors. If those other two people match each other, it can be on a segment where you don’t match either of them, and thanks to an ancestor that they share who isn’t in your line at all. Shared matches are a great hint, especially in addition to other information, but shared matches don’t necessarily mean triangulation although it’s a great place to start looking.
I have shared matches where I match one person on my maternal side, one on my paternal side, and they match each other through a completely different ancestor on an entirely different segment. However, we don’t triangulate because we don’t all match each other on the SAME segment of DNA. Yes, it can be confusing.
Just remember, each of your segments, and matches, has its own individual history.
Imputation Can Affect Matching
Over the years the chips on which our DNA is processed at the vendors have changed. Each new generation of chips tests a different number of markers, and sometimes different markers – with the overlaps between the entire suite of chips being less than optimal.
I can verify that most vendors use imputation to level the playing field, and even though two vendors have never verified that fact, I’m relatively certain that they all do. That’s the only way they could match to their own prior “only somewhat compatible” chip versions.
The net-net of this is that you may see some differences in matching segments at different vendors, even when you’re comparing the same people. Imputation generally “fills in the blanks,” but doesn’t create large swatches of non-existent DNA. I wrote about the concept of imputation here.
What I’d like for you to take away from this discussion is to be focused on the big picture – if and how people triangulate which is the function important to genealogy. Not if the start and end segments are exactly the same.
Each of the major vendors, except Ancestry who does not have a chromosome browser, offers some type of triangulation solution, so let’s look at what each vendor offers. If your Ancestry matches have uploaded to GedMatch, Family Tree DNA or MyHeritage, you can triangulate with them there. Otherwise, you can’t triangulate Ancestry results, so encourage your Ancestry matches to transfer.
I wrote more specifically about triangulation here and here.
Let’s start by looking at triangulation at MyHeritage.
Triangulation at MyHeritage
MyHeritage offers triangulation integrated into their chromosome browser.
At MyHeritage, select DNA Matches from the DNA dropdown menu, then click on the purple “Review DNA Match” of the person you want to compare. We re looking at my cousin, Cheryl F.
When reviewing my DNA match with Cheryl, I can see the list of people that Cheryl and I both match, including my mother, first on the list. In addition to my mother’s relationship to me, I can also see an estimate of how closely my mother matches the other person – in this case, Cheryl. Cheryl is my mother’s first cousin (1C) and my first cousin, once removed (1C1R.)
For triangulation, the important image is the little purple icon at right, above.
Clicking on the purple triangulation icon shows the segments where Cheryl, my mother and I all three match and triangulate.
Finding my mother among Cheryl’s close matches tells me immediately which parent I share with Cheryl.
The areas on the chromosome browser below in the rounded squares are triangulated, meaning that I match Cheryl and the other person (who just happens to be my mother) on that same segment.
Showing triangulation with Cheryl and my mother provides a great example, because of course I triangulate with Cheryl and my mother on every segment where I match Cheryl – because I inherited all of those segments through my mother.
However, as far as triangulation goes, the fact that two of those people are closely related, me and my mother, makes it the same as only two people matching – Mom and Cheryl. Still, since Mom and Cheryl are first cousins, that match confirms my great-grandparents.
Cheryl carries pieces of my great-grandparent’s DNA that my mother doesn’t though, so matches in common with Cheryl may prove very genealogically useful.
At the top right of this chromosome browser page, I can “add or remove DNA matches” from my match list. I can look through my match list to find another close relative to see if they triangulate or I can download my match list to see who else matches me on that same segment. Instructions for the file download are at the end of this section.
Same Segment Matches
To illustrate that people will match you on the same segment, but don’t match each other because they descend from different sides of your family, I’ll add some cousins from my father’s side of the family.
I’m going to select cousins Charlene and David, and remove my mother.
Below, we show chromosome 3 again, but the triangulation bracket is gone. This tells us that this segment does NOT triangulate between me and ALL three people.
Please note that I may triangulate with some of the people. The absence of the bracket only means that I don’t triangulate with ALL of them.
I already know that while I match Cheryl, Charlene and David on this segment, only David and Charlene match each other because they are both from my father’s side, and Cheryl doesn’t match either of them because she is on my mother’s side.
To prove this, and to determine triangulation groups, I can compare the people two by two and continue adding people to see if they continue to triangulate.
Below, I’ve removed Cheryl, and I triangulate on chromosome 3 with both Charlene and David. The triangulation bracket appears.
Therefore, I know that Charlene and David descend through one of my parents, and Cheryl through the other – even if I didn’t know anything else at this point.
To reiterate, triangulation at MyHeritage means triangulation with everyone showing at the same time on the chromosome browser.
Other Resources to Identify Common Ancestors
For additional information, I can check the match information with each person to see if our trees, surnames or locations intersect.
SmartMatches and Theories of Family Relativity each provide clues and help to explain why we might triangulate.
SmartMatches tell you that you and another person share an ancestor in your and their tree, BUT, that common person may not be a direct ancestor of one or both of you. You also may or may not be DNA matches, and if so, your DNA match may or may not be through that ancestor.
Theories of Family Relativity (TOFR,) on the other hand, tell you that not only do you have a DNA match with this person, but that you have a common ancestor, and who that ancestor is. Sometimes the connection is made for you, even if one or both of you don’t show that ancestor in your tree simply because you have not extended your tree back far enough in time.
I wrote about how to use Theories of Family Relativity here.
You can request to download your matches list and also your shared DNA segments at MyHeritage by clicking on the three dots to the right at the top of your match list, then click on the option you wish. The resulting files will be e-mailed to you a few minutes later. If they don’t arrive, be sure to check your spam filter.
Downloading your match list and/or shared DNA segments is NOT the same thing as downloading your raw data file to upload elsewhere. You’ll find those instructions in the Transfer section later in this article.
What About You?
Do you have a tree at MyHeritage?
If not, click on Family Tree to create or upload one including not only direct line ancestors, but their children and grandchildren which facilitates and encourages the formation of Theories of Family Relativity.
Connecting Your DNA to Your Tree
Assigning your kit and those of family members to the proper profile card in your tree is very important, especially for the formation of Theories of Family Relativity
To suggest a theory, MyHeritage searches through all the possible links in the MyHeritage database meaning SmartMatches between trees, Record matches, record to record matches, etc.
If a DNA kit is not associated with an individual that is connected to ancestors, this reduces the probability that MyHeritage will be able to find a theory.
For example, if I took a DNA test but only have myself in the tree, not connected to my father and mother, but my father appears in another user’s tree (and there are more ancestors in that tree) MyHeritage won’t be able to find the information to generate a theory.
If I add my father, then the system has a common ancestor to work with.
When the TOFR algorithm runs, it’s trying to find any possible route to connect the two individuals (you and your DNA Match). If you are associated with individuals in multiple sites or trees, MyHeritage will try all of them and generate multiple paths for you to evaluate.
Have you assigned the kits of family members you manage to the proper place in your tree?
You can do this easily under the Manage DNA Kits option, under the DNA tab. Click on the three little dots to the right of the kit.
Then click assign the kit.
You’ll be prompted
If you start typing, you’ll be prompted with the names of people in your tree.
Other Resources to Identify Common Ancestors
MyHeritage includes other tools to help you identify common ancestors as well, including:
- SmartMatches where MyHeritage matches individuals in trees
- AutoClusters showing groups of people that match you and each other
- Shared Matches indicating common DNA matches between you and another DNA match
- Shared Ancestral Surnames show common surnames, even if a common ancestor does not show in a tree
- Shared Ancestral Places indicating common locations in trees
- Shared Ethnicities comparing ethnicity between matches, a feature typically only beneficial if looking for a minority (to you) ancestry match
- Genealogical Records including matches from other databases such as Geni.com and FamilySearch
Have you tested family members, especially everyone in the older generations? You can transfer their kits from Ancestry, 23andMe or FamilyTreeDNA if they’ve already tested there to MyHeritage.
The article, Are You DNA Testing the Right People? explains how to determine who to test. Make sure you aren’t missing anyone that you need.
Here’s how to transfer:
- Ancestry Step by Step Guide: How to Upload-Download DNA Files
- 23andMe Step by Step Guide: How to Upload-Download DNA Files
- MyHeritage Step by Step Guide: How to Upload-Download DNA Files
- Family Tree DNA Step by Step Guide: How to Upload-Download DNA Files
I wrote recently about how to work with triangulation at FamilyTreeDNA. Join me soon for similar articles about how to work with triangulation at 23andMe, GedMatch and DNAPainter.
Most of all – have fun!
I receive a small contribution when you click on some of the links to vendors in my articles. This does NOT increase the price you pay but helps me to keep the lights on and this informational blog free for everyone. Please click on the links in the articles or to the vendors below if you are purchasing products or DNA testing.
Thank you so much.
DNA Purchases and Free Transfers
- MyHeritage DNA only
- MyHeritage DNA plus Health
- MyHeritage FREE DNA file upload
- 23andMe Ancestry
- 23andMe Ancestry Plus Health
- Legacy Tree Genealogistsfor genealogy research
Too bad Ancestry won’t supply chromosome matching data!
It sure is.
It appears to me that David and Cheryl triangulate on more segments (1, 3, & 4). Why are they from different parents (but Charlene only on chromosome 3). To triangulate, does it have to be the exact same start and end points? Not just some overlap?
I don’t understand the question in the first part. Can you restate that part. As for the second part, no, the start and end does not need to be identical but the overlapping part needs to reach a specific threshold.
It looks to me like David and Cheryl have segments in common on chromosomes 1, 3, & 4. Why is there no triangulation bracket. Chromosome 4 in particular seems like there is a rather large segment in common. I can understand if 1 & 3 maybe don’t meet threshold, but on 4 there is a greater overlap that what Charlene and David share on chromosome 3. This is confusing to me.
Yes, that’s accurate. There are two points. First, all 3 of these people match ME on this segment – but I have 2 chromosomes – 1 from my father and one from my mother. So while Charlene and David match me on my father’s chromosome, Cheryl matches me on exactly the same segment on my mother’s chromosome. So David and Charlene would triangulate when only those two are shown on MY chromosome browser. This is how you know who matches you on the same side of your tree – they will triangulate. The second point is that when multiple people are shown on a browser, the triangulation bracket will only appear when ALL of the people triangulate with you. If the bar is absent, remove people until the bracket appears and you’ll know who is and is not on the same side of your tree.
Roberta, have you ever run across this situation using MyHeritage triangulation? (I’ll use your cousins’ names as examples). I start with a group of 3 matches to my mom, and there’s no triangulation group as in your example. I then remove “Cheryl” which creates the triangulation bracket with “Charlene” and “David”. So far, so good. But then, I’ll swap out “Charlene” for “Cheryl” which creates the triangulation bracket for “Cheryl-David”. Then I try swapping out “David” for “Charlene” and find a triangulation bracket for “Cheryl-Charlene”. It makes no sense to me — unless I’m missing something.
It’s possible if the segments don’t overlap exactly that the matching portion of the segments does not reach the threshold for all 3 if they are stacked up. That’s the only possibility I see. I would suggest contacting support.
Wondering if you ever got help from MyHeritage on this or an explanation? I am working with large segments, 20cM and greater, with a lot of overlap and am having similar issues. In this case it should not be a threshold problem as the segments are almost completely overlapping and large. Person A and Person B form a triangulation group. Person A and Person C form a triangulation group, but Person B and Person C do not form a triangulation group. As both B and C triangulate with person A over the same segment, this seems impossible to me. It seems as though there is a bug in their system. I have run across this on multiple segments on different chromosomes now. Thanks for any light you can shed on this issue.
I would suggest contacting support. Please let us know what they say.
So fun, Roberta!! I know it’s been a couple weeks since your MH triangulation article was published, but when I’ve had a minute, I’ve been playing around with a few triangulation groups that sort of overlap, and some that are side-by-side. So say there are a number of triangulation groups sitting side-by-side….is it possible that other cousin matches that overlap and share part of some of the same triangulation groups, but not all of them, might have a different path to the same ancestral couple that their neighboring triangulation group might go to, but not in the same way, if the respective triangulation boundaries differ a bit? Like, a lot? Or do you think not only the paths, but the ancestral couples, are completely different? Say my Smith/Jones ancestor couple I share with a particular triangulation group is known (to me, through my research on my tree) to come down to me through 7 generations. But I have another branch that is somewhat unknown, and it’s possible that there is another path up to that couple. Is it possible I also am a descendant of the Smith/Jones couple through another path, and that possibly a neighboring triangulation group gives evidence of this? Does that ever happen?
Try the genetic clusters to see what you can discover. Also, download your matches and see what else you can discover in terms of which people match nearby. Nearby results could be the same couple or someone different entirely.
So are Autoclusters in MH indicating that all the people in the Autocluster triangulate?
No, they indicate that they match each other. The marches can be on different segments.
Oh! Thank you! I’m searching for my paternal GF’s missing ancestors for my 89 year old Dad. Am able to group a lot of mutual matches all falling from the same couple, on different platforms (annoying). And Dad’s strongest match in this large group is only on MyHeritage. In her mutual match list up high is another strong match also only on MyHeritage and both of these falling from this same couple. But I’ve been baffled, as they don’t triangulate according to MH. And I expected they would.They are put together in a cluster though. I have noticed where segments are on Dad’s chromosomes for each of these, they do not overlap. So I’m wondering if this could be why I don’t see triangulating icon with these two? And seeing your answer above, people in clusters fm MH don’t triangulate, are just in common with; I’m wondering what the relevance of it now. Oh hang on. Suppose it would be because people in mutual match lists won’t necessarily match each other, but when my heritage puts them into clusters, these are the ones that do match each other? I think I may have answered my own question? I would like an answer to question about if people on mutual match list do match each other eg through same couple, but there is no triangulation between the two at top and one in list, where segments don’t overlap could this explain why? And lastly. when painting chromosomes and in above scenario where people share, I’ll call them targeted ppl in trees, as in above situation.I know these match’s should go on the paternal side of Dad’s chromosome ie not the side all of his known cousins occupy, but I can recognise all of these in same group? And I hope I haven’t lost you with that last one.
I’m sorry. I can’t follow this. You can contact support. They can look at your account so they will be able to see.
Roberta, thank you for this; it’s very helpful. All of your posts are helpful. Thanks for sharing with us. 🙂
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Roberta, I watched the myheritage facebook live yesterday. and you spoke about the cluster tool – I noted that you said the top 4 clusters would likely be your 4 great grandparents. Did I misunderstand that. Was hoping to find more info here re: the myheritage cluster tool but haven’t found it yet.
Yes, that’s what is generally found. Use the search box and look for “Leeds” and Genetic Affairs.” The cluster tool at MH is theirs.
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I think I have a triangulation but want to be sure. At MH I match with two 3rd cousins on Chromosome 1. These matches are at least 21cMs in length. I have found a number of other matches that match myself and my cousins on the same segment of chromosome 1. Some of the matches are longer than 21cMs but I do have an orange square that surrounds 21cMs of all the matches. For many of these matches I do not have a pedigree chart, even so would it be true for me to say we all match and are somehow related??
Yes, that’s accurate. It would be very unusual for a segment that large to be IBC but it’s theoretically possible.
My brother and his 3rd cousin share a match on FTDNA with a Ms Swaim. (both are managed by me). My brother shares 31cMs with Ms Swaim and his cousin shares 48cMs with Ms. Swaim, also all 3 triangulate on chromosome 19 with a segment length of 7.7cMs.
I have transferred both to My Heritage. But on My Heritage Ms Swaim does not show up on my brother’s match list. Ms. Swaim does however show up as a match for our cousin.
Why do you think Ms Swaim does not show up as a match for my brother?
The only thing I can think of is imputation gone awry, but otherwise I don’t know. It seems odd.
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Hi Roberta I am a member of MyHeritage and recently my Cousin in Hungary who is my Fathers Great Niece or my 1st Cousin once removed put her DNA up in the site. I got a shock when my mother who is of mainly English background came up as a match to my Fathers Great Niece it came up as 3rd to Distant Cousin (low confidence). My mother my 1st Cousin once removed and I came up as a triangulation on line 19 of the segment lines. I have a very extensive family tree and have discovered a Hungarian relative to my mother which from memory goes back to the 1600s. Is it possible that My first Cousin once removed my mother and myself share a common relative from the distant past which from my understanding would be through my Cousins Father or Grandmother as my father is her Grandfathers brother.
Hi Roberta, I have a question. I triangulate with my cousin Wendell and Sherri M. at MH. Sherri has had both of her parents tested. But Wendell and I do not triangulate with either of her parents. Is this a mistake? Thanks! Jeff
If this is a valid match, you should match one of her parents.
Thanks for all you do.
I have done genealogy for over 40 years but recently have gotten into the DNA aspect
of research. Unfortunately, my dad passed away before I could get him tested. That has bothered me greatly.
I have tested my mom, brother and my dad’s brother. Do I have the following correct?
1. Between my brother and I, we inherited about 75% of my dad’s DNA
2. Any matches that I have that do not match with my mom, my brother or my dad’s brother would have matched my dad.
No, that’s not correct. They likely would not have matched your Dad. Between all those people, you have a lot of your Dad’s DNA. People who don’t match any of you might have matched your Dad, but they may also be identical by chance.
I have a question. My Uncle Harold matches Amanda (64.2 cM) and Amanda’s mother Norma (47.6 cMs). As my Uncle has a stronger match with Amanda
than with Amanda’s mother, does that mean that my Uncle would also have a match with Amanda’s paternal line too?
My dad’s family is from Southeastern Kentucky. I really think we ALL connect somehow!!
Possibly. Part could also be identical by chance and depending on which vendor, influenced by imputation.
Another question about triangulation. My mother has a match that has a total of 74 cMs. This match is all on one segment of 74 cMs in length on chromosome 10. She triangulates with this match with another match. The three triangulate on chromosome 10 with a length of 67 cMs. My issue is that I have the complete pedigree charts for all 3 back 6 generations but there is not a common ancestor among them. I was thinking with a triangulation of a segment of 67cMs in length that a common ancestor would be found among them within 6 generations??? What are your thoughts?
Yes, generally I would think so. But there are unknown ancestors. Plus, sometimes imputation dies strange things. I’d suggest uploading the DNA files to FamilyTreeDNA to see if they still match each other on that entire segment.
On MyHeritage my mom triangulates with my brother David and I on Chromosome 1 with a distance of 21 cMs.
My mom and I triangulate with E.B. on this same segment and with the same distance. But there is no triangulation when my brother is added. Does this mean that E.B. also matches my dad as my brother does not triangulate with us?
Sometimes their triangulation just doesn’t work quite right.
Hey Roberta, on MyHeritage I match 7 people and we all match each other, we triangulate! yea!!! All 7 matches are from the same area of South Carolina. The length of the segment that all 8 of us match is only 7cMs. Does the fact that 8 of us triangulate reduce the likelihood that the match could be by chance?
Yes, so long as the 7 people aren’t all your close family.