Identifying Unknown Parents and Individuals Using DNA Matching

There have been a lot of questions recently about the methodology used by people searching for unknown parents and other unidentified individuals. I covered this technique in concept recently at a conference as part of an overview presentation. In this article, I’m addressing only this topic and in more detail.

What is the methodology that genealogists use to identify unknown parents? It’s exactly the same process used to identify unknown Does, meaning unidentified bodies as well as violent criminals who have left DNA, such as blood or semen, at a crime scene.

How is Identifying Unknown Individuals Different from Genealogy?

Genealogists are interested in discovering their ancestors. Generally, genealogists know who their parents are and most of the time, their grandparents as well. Not very many people can tell you the names of their great-grandparents off the top of their head – not unless they ARE genealogists😊

Genealogists interview family members and access family sources, such as photos, Bibles, boxes of memorabilia and often extend their family another generation or two using these resources. Then, to gather additional information, genealogists turn to publicly available sources such as:

Constructing a Tree

Genealogists utilize software to create trees of their ancestors, either on their own computers with software such as Family Tree Maker, Legacy, RootsMagic or the free tree building software from MyHeritage. They then either synchronize or duplicate their tree on the public sites mentioned above which provide functionality such as “hints” that point to documents relevant to the ancestors in their tree. Additionally, they can access the trees of other genealogists who are researching the same ancestors. This facilitates the continued growth of their tree by adding ancestors and extending the tree back generations.

While tree-building is the goal of genealogists, the trees they build are important tools for people seeking to identify unknown individuals.

The Tree

Generations tree

In my tree, shown in the format of a pedigree chart, above, you can see that I’ve identified all 16 of my great-great-grandparents. In reality, because I’ve been a genealogist for decades, I’ve identified many more of my ancestors which are reflected in my tree on my computer and in my trees at both Ancestry and MyHeritage where I benefit from hints and DNA matches.

Genealogical pedigree charts are typically represented with the “home person,” me, in this case at the base with my ancestors branching out behind them like a lovely peacock’s tail.

While I’m looking for distant ancestors, adoptees and others seeking the identities of contemporary people are not looking back generations, but seek to identify contemporary generations, meaning people who are alive or lived very recently, typically within a generation.

Enter the world of genetics and DNA matching.

Genetics, The Game Changing Tool

Before the days of DNA testing, adoptees could only hope that someone knew the identify of their biological parents, or that their biological parents registered with a reunion site, or that their court records could be opened.

DNA testing changed all of that, because people can now DNA test and find their close relatives. As more people test, the better the odds of actually having a parent or sibling match, or perhaps a close relative like an aunt, uncle or first cousin. My closest relative that has tested that I didn’t know was testing is my half-sister’s daughter.

You share grandparents with your first cousin, and since you only have 4 grandparents, it’s not terribly difficult to figure out which set of grandparents you connect to through that first cousin – especially given the size of the databases and the number of matches that people have today.

The chart below shows my matches as of June 2019.


Total Matches

Second Cousin or Closer

Family Tree DNA












You can see that I have a total of 45 close matches, although some of those matches are duplicates of each other. However, each database has some people that are only in that database and have not tested at other companies or transferred to other databases.

Situations like this are exactly why people who are searching for unknown family members take DNA tests at all 4 of the vendors.

Stories were once surprising about people who tested and either discover a previously unknown close relative, or conversely discovered that they are not related to someone who they initially believed they were. Today these occurrences are commonplace.


If you’re searching for an unknown parent or close relative, you just might be lucky to receive a parental, sibling, half-sibling or uncle/aunt match immediately.

An estimated relationship range is provided by all vendors based on the amount of DNA that the tester shares with their match.

Generations Family Tree DNA matches

My mother’s match page at Family Tree DNA is shown above. You can see that I’m Mother’s closest match. My known half brother did not test before he passed away, and mother’s parents are long deceased, so my mother should NEVER have another match this close.

So, who is that person in row 2 that is also predicted to be a mother or daughter? I took a test at Ancestry and uploaded my results to Family Tree DNA for research purposes, so this is actually my own second kit, but for example purposes, I’ve renamed myself “Example Adoptee.” Judging from the photo here, apparently my “adopted” sibling was a twin😊

If the adoptee tested at Family Tree DNA, she would immediately see a sibling match (me) and a parent match (Mom.) A match at that cM (centiMorgan) level can only be a parent or a child, and the adoptee knows whether she has a child or not.

Let’s look at a more distant example, which is probably more “typical” than immediately finding a parent match.

Let’s say that the “male adoptee” at the bottom in the red box is also searching for his birth family. He matches my mother at the 2nd-3rd cousin level, so someplace in her tree are his ancestors too.

People who have trees are shown with gold boxes around the tiny pedigree icons, because they literally are trees of gold.

Because of Family Tree DNA’s “bucketing” tool, the software has already told my Mother that the male adoptee is a match on her father’s side of her tree. The adoptee can click on the little pedigree icon to view the trees of his matches to view their ancestors, then engage in what is known as “tree triangulation” with his other close matches.

From the Perspective of the Adoptee

An adoptee tests not knowing anything about their ancestors.

Generations adoptee

When their results come back, the adoptee, in the red box in the center, hoping to identify their biological parents, discovers that their closest matches are the testers in the pink and blue ovals.

The adoptee does NOT know that these people are related to each other at this point, only that these 7 people are their closest matches on their match list.

The adoptee has to put the rest of the story together like a puzzle.

Who Matches Each Other?

In our scenario, test takers 2, 3 and 8 don’t match the adoptee, so the adoptee will never know they tested and vice versa. Everyone at a second cousin level will match each other, but only some people will match at more distant relationships, according to statistics published by 23andMe:

Relationship Level

Percentage of People Who Match

Parents, siblings, aunts, uncles, half siblings, half aunts/uncles and 1st cousins


2nd cousins


3rd cousins


4th cousins


5th cousins


6th cousins and more distant


You can view a detailed chart with additional relationships here.

Tree Triangulation

By looking at the individual trees of test taker 1, 4 and 5 whom they match, the adoptee notices that John and Jane Doe are common ancestors in the trees of all 3 test takers. The adoptee may also use “in common with” tools provided by each vendor to see who they match “in common with” another tester. In this case, let’s say that test taker 1, 4 and 5 also match each other, so the adoptee would also make note of that, inferring correctly that they are members of the same family.

The goal is to identify a common ancestor of a group of matches in order to construct the ancestor’s tree, not a pedigree chart backwards in time, as with genealogy, but to construct a descendants’ tree from the ancestral couple to the current day, as completely as possible. After all, the goal is to identify the parent of the adoptee who descends from the common ancestor.

Generations adoptee theory

In this case, the adoptee realized that the pink test takers descended from John and Jane Doe, and the blue test takers descended from Walter and Winnie Smith, and constructed descendant trees of both couples.

The adoptee created a theory, based on the descendants of these two ancestral couples, incorporating other known facts, such as the year when the adoptee was born, and where.

In our example, the adoptee discovered that John and Jane Doe had another daughter, Juanita, whose descendants don’t appear to have tested, and that Juanita had a daughter who was in the right place at the right time to potentially be the mother of the adoptee.

Conversely, Walter and Winnie Smith had a son whose descendants also appear to have not tested, and he had a son who lived in the same place as Juanita Doe. In other words, age, opportunity and process of elimination all play a role in addition to DNA matches. DNA is only the first hint that must be followed up by additional research.

At this point, if the adoptee has taken either Y or mitochondrial DNA testing, those results can serve to either include or exclude some candidates at Family Tree DNA. For example, if the adoptee was a male and matched the Y DNA of the Smith line, that would be HUGE hint.

From this point on, an adoptee can either wait for more people to test or can contact their matches hoping that the matches will have information and be helpful. Keep in mind that all the adoptee has is a theory at this point and they are looking to refine their theory or create a new one and then to help narrow their list of parent candidates.

Fortunately, there are tools and processes to help.

What Are the Odds?

One helpful tool to do this is the WATO, What Are the Odds statistical probability tools at DNAPainter.

Using WATO, you create a hypothesis tree as to how the person whose connection you are seeking might be related, plugging them in to different tree locations, as shown below.

Generations WATO

This is not the same example as Smith and Doe, above, but a real family puzzle being worked on by my cousin. Names are blurred for privacy, of course.

Generations WATO2

WATO then provides a statistical analysis of the various options, with only one of the above hypothesis being potentially viable based on the level of DNA matching for the various hypothetical relationships.

DNAPainter Shared cM Tool

If your eyes are glazing over right about now with all of these numbers flying around, you’re not alone.

I’ll distill this process into individual steps to help you understand how this works, and why, starting with another tool provided by DNAPainter, the Shared cM tool that helps you calculate the most likely relationship with another person.

The more closely related you are to a person, the more DNA you will share with them.

DNAPainter has implemented this tool based on the results of Blaine Bettinger’s Shared cM Project where you can enter the amount of DNA that you share with someone to determine the “best fit” relationship, on average, plus the range of expected shared DNA.

Generations DNAPainter Shared cM Project

You, or the test taker, are in the middle and the relationship ranges surround “you.”

For example, you can clearly see that the number of cMs for my Example Adoptee at 3384 is clearly in the Parent or Child range. But wait, it could also be at the very highest end of a half sibling relationship. Other lower cM matches are less specific, so another feature of the DNAPainter tool is a life-saver.

At the top of the page, you can enter the number of matching cMs and the tool will predict the most likely results, based on probability.

Generations 3384

The relationship for 3384 cMs is 100% a parent/child relationship, shown above, but the sibling box is highlighted below because 3384 is the very highest value in the range. This seems to be a slight glitch in the tool. We can summarize by saying that it would be extremely, extremely rare for a 3384 cM match to be a full sibling instead of a parent or child. Hen’s teeth rare.

Generations parent child

Next, let’s look at 226 cM, for our male adoptee which produces the following results:

Generations 226

The following chart graphically shows the possible relationships. The “male adoptee” is actually Mom’s second cousin. This tool is quite accurate.

Generations 226 chart

Now that you’ve seen the tools in action, let’s take a look at the rest of the process.

The Steps to Success

The single biggest predictor of success identifying an unknown person is the number of close matches. Without relatively close matches, the process gets very difficult quickly.

What constitutes a close match and how many close matches do adoptees generally have to work with?

If an adoptee matches someone at a 2nd or 3rd cousin level, what does that really mean to them?

I’ve created the following charts to answer these questions. By the way, this information is relevant to everyone, not just adoptees.

In the chart below, you can view different relationships in the blue legs of the chart descending from the common ancestral couple.

In this example, “You” and the “Other Tester” match at the 4th cousin level sharing 35 cM of DNA. If you look “up” the tree a generation, you can see that the parents of the testers match at the 3rd cousin level and share 74 cM of DNA, the grandparents of the testers match at the 2nd cousin level and share 223 cM of DNA and so forth.

Generations relationship table

In the left column, generations begin being counted with your parents as generation 1. The cumulative number of direct line relatives you have at each generation is shown in the “# Grandparents” column.

Generations relationship levels

Here’s how to read this chart, straight across.

Viewing the “Generation” column, at the 4th generation level, you have 16 great-great-grandparents. Your great-great-grandparent is a first cousin to the the great-great-grandparent of your 4th cousin. Their parents were siblings.

Looking at it this way, it might not seem too difficult to reassemble the descendancy tree of someone 5 generations in the past, but let’s look at it from the other perspective meaning from the perspective of the ancestral couple.

Generations descendants

Couples had roughly 25 years of being reproductively capable and for most of history, birth control was non-existent. If your great-great-great-grandparents, who were born sometime near the year 1800 (the births of mine range from 1785 to 1810) had 5 children who lived, and each of their descendants had 5 children who lived, today each ancestral couple would have 3,125 descendants.

If that same couple had 10 children and 10 lived in each subsequent generation, they would have 100,000 descendants. Accuracy probably lies someplace in-between. That’s still a huge number of descendants for one couple.

That’s JUST for one couple. You have 32 great-great-great-grandparents, or 16 pairs, so multiply 16 times 3,125 for 50,000 descendants or 100,000 times 16 for…are you ready for this…1,600,000 descendants.

Descendants per GGG-grandparent couple at 5 generations Total descendants for 16 GGG-grandparent couples combined
5 children per generation 3,125 50,000
10 children per generation 100,000 1,600,000

NOW you understand why adoptees need to focus on only close matches and why distant matches at the 3rd and 4th cousin level are just too difficult to work with.

By contrast, let’s look at the first cousin row.

Generations descendants 1C.png

At 5 descendants per generation, you’ll have 25 first cousins or 100 first cousins at 10 descendants per generation.

Generations descendants 2C

At second cousins, you’ll have 125 and 1,000 – so reconstructing these trees down to current descendants is still an onerous task but much more doable than from the third or fourth cousin level, especially in smaller families.

The Perfect Scenario

Barring a fortuitous parent or sibling match, the perfect scenario for adoptees and people seeking unknown individuals means that:

  • They have multiple 1st or 2nd cousin matches making tree triangulation to a maternal and paternal group of matches to identify the common ancestors feasible.
  • Their matches have trees that allow the adoptee to construct theories of how they might fit into a family.

Following the two steps above, when sufficient matching and trees have been assembled, the verification steps begin.

  • Adoptees hope that their matches are responsive to communications requesting additional information to either confirm or refute their relationship theory. For example, my mother could tell the male adoptee that he is related on her father’s side of the family based on Family Tree DNA‘s parental “side” assignment. Based on who else the adoptee matches in common with mother, she could probably tell him how he’s related. That information would be hugely beneficial.
  • In a Doe situation where the goal is to identify remains, with a relatively close match, the investigator could contact that match and ask if they know of a missing family member.
  • In a law enforcement situation where strong close-family matches that function as hints lead to potential violent crime suspects, investigators could obtain a piece of trash discarded by the potential suspect to process and compare to the DNA from the crime scene, such as was done in the Golden State Killer case.

If the discarded DNA doesn’t match the crime scene DNA, the person is exonerated as a potential suspect. If the discarded DNA does match the crime scene DNA, investigators would continue to gather non-DNA evidence and/or pick the suspect up for questioning and to obtain a court ordered DNA sample to compare to the DNA from the crime scene in a law enforcement database.

Sometimes DNA is a Waiting Game

I know that on the surface, DNA matching for adoptees and unknown persons sounds simple, and sometimes it is if there is a very close family match.

More often than not, trying to identify unknown persons, especially if the tester doesn’t have multiple close matches is much like assembling a thousand-piece puzzle with no picture on the front of the box.

Sometimes simply waiting for a better match at some point in the future is the only feasible answer. I waited years for my brother, Dave’s family match. You can read his story here and here.

DNA is a waiting game.



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30 thoughts on “Identifying Unknown Parents and Individuals Using DNA Matching

  1. if i send a copy of my dna profile,, and my daughters,, can anyone with the skill to do so,, produce a dna profile of the father of my child?? if so,,please contact me,,bclands@telus,net

      • she was not adopted, He ran, I have gone onto the gedmatch site and tried to upload our dna profiles,, the ones i sent you, And i did try to upload to family tree, It will not accept the report, It keeps asking for the digitized report, The report is the one i provided, I do not know how to do this,, I need very much to upload the report, could you perhaps have a look at it and tell me what is missing???

        • Sandra, did you download your raw data file from where you tested? That’s what you need. DNAadoption is not just for adoptees and they have people to help you for free.

    • Hmmm, dna profile – maybe.
      Region profile might be easier.
      Upload both mum and daughter to gedmatch and make phased kits.
      Use the daughters P1 paternal phased kit to look for matches in the 3000 list [ aka one to many ] and look for common email addresses, eg donegal xxx @ yyy. com. See if you can meet up with an experienced person[s] to help.

  2. Hi Roberta – Great article. It was forwarded to those I know either assisting or needed for personal use.

    Great job – Thank You Again for Sharing Your Talents ♡

    Love You – Ally n Cali

  3. Hi Roberta
    We are connected through our respective Miller families. I learned this while doing extensive research searching for my mom’s Biological parents. We did not know my mom was adopted until May, 2017. This is when her results were returned from her FTDNA kit. She had close family matches to people we had never heard of. I had done the FTDNA test 2 years prior to this and had close matches to people I had never heard of either. Therefore, I did the other three major DNA tests. I also had my sister do the FTDNA test with the same results. All of the tests had people I did not know showing as close family matches. We are all from SW lower Michigan and these people were from the Southeast, Southwest, and Northwest. She even had matches from England and Sweden. There were some from the Pennsylvania area where her assumed family came from, so I ignored mine. My dad’s side is predominantly from the Northeast.
    I have been doing real honest Genealogy work and Family Trees with Family Tree Software since 1990. I have travelled to many states to gather what I thought was pertinent information for my family. Then mom’s DNA results came back. We sent for her Certified Adoption Records and sure enough, she was adopted. She was 83 when she found out and is now 85. We now had vague names to go by. The clincher was when my assumed cousins did their DNA and we did not match at all. We now know they are my adopted cousins.
    Thanks to my many years of genealogy experience and the DNA matches, I was able to find her biological family. They have been receptive for the most part.
    Mom’s family is from Utah via England and Sweden on her maternal side and Germany, Ireland, Scotland, Pennsylvania, North Carolina, Indiana, Illinois, and finally Missouri, on her paternal side. Her father and mother ended up in Michigan together at the same time by coincidence.
    Cheri Gates Shepherd

  4. In this article you say, “That’s JUST for one couple. You have 32 great-great-grandparents, or 16 pairs, so multiply 16 times 3,125 for 50,000 descendants or 100,000 times 16 for…are you ready for this…1,600,000 descendants.”

    Perhaps I am mistaken but I believe you meant to say either “you have 16 great-great grandparents” or “”you have 32 great-great-great grandparents”

  5. Excellent, informative article.
    Yes, it is a massive jigsaw puzzle, but look for common email addresses, eg Donegal, and regions, etc in gedmatch can narrow it down dramatically. Such regions should also co-incide with Ancestry region maps.

  6. Thanks, Roberta, for a clear and thorough article. I’d like to share it with all the cousins whose DNA tests I’m working on, but couldn’t find a “share” option. Is it okay if I post the link to Facebook to share? Or ?

    • There should be share buttons st the bottom of the post in the blog page, not the delivery email. I will be sure they are still there. However, it’s always fine to share posts by copying the links. And thank you.

  7. Good stuff! Enjoyed hearing this from someone experienced. Wish I had this article a few years ago when I started searching for my birth parents with almost no information. It was not until DNA came along that I had a chance. I still had to pretty much figure out the bits of trial trees and triangulation. But the key for me was a first cousin that I matched that had a sister with a great family tree. After locating about 20 matches on the tree the picture started to come together and narrowed down to two sisters. One of whom lived where I was born. An important part of this was for me to test with all the major companies and then upload to others that allowed it. My matches were not just on one site and it took several tests to get the complete picture.

    I did have to get over one bump in the road because I could find no matches at all on my mother’s husband’s side. As it turns out it was one of those DNA surprises. My mother lied on my adoption papers and identified her husband as my father. DNA tests showed otherwise and through a similar set of matches with first cousins I identified my birth father’s family. So you cannot always rely on official records. Sometimes they are false.

    It is now a little late in life as both of my parents and their siblings are already gone but I have connected with some cousins and was able to get first hand stories about them.

    Also; I had close DNA match contact me with a similar story of being adopted and it was through her match to me and my tree that she was able to find her birth mother who is one of my first cousins. We were able to get them reunited. I never thought I would be the missing DNA link to a family I didn’t know.

    Keep up the great blogs. I learn a lot.

  8. i have a dna profile of myself and my daughter, The work was done by ancestry, i would like to post myself and her on whatever site i need to,, to find her fathers match, how do i do this,

  9. Thank you for this info, although it was more than I could digest all at once!
    I am using Ancestry to help an adopted friend look for his birth father, and I’m wondering if you have thoughts on my methodology. We have the advantage of a known birth mother. She hasn’t tested, but we have a DNA match to her 1st cousin. I put the cousin and most of his shared matches in a birth mother group, as well as shared matches of the shared matches, although I eventually stopped grouping those sharing less than 40cM.
    Returning to the larger list of DNA matches, if Cousin X’s shared matches included people in the birth mother group, I added Cousin X to the birth mother group, along with their previously ungrouped shared matches.
    Now all second cousins and nearly every third cousin is marked as birth mother group. Of those not grouped, if I go to their shared matches, there are tons marked birth mother group. So this has been a useless exercise, but I’m wondering if it is because my methodology was inherently flawed, or if it simply indicates that the cousin I started with shares DNA with both birth parents. Any insights would be appreciated!

    • I would try the Leeds method. You might also try auto-clusters. The parents may be related or from a common or endogenous population too. Visit www.

  10. My #1 relative turned out to be a half sister. So great. My second listed relative is a first cousin with 12.8 DNA shared. You said that first cousins share grandparents, but I am 74 and she is 28. Could she be a grandchild instead? It seems impossible that we would share grandparents with the age difference. I have no idea who my father is. Trying to use your article to find out. Thank you!

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  12. Hi – is it meaningful if a person has double the number of DNA matches on one unknown parent’s side compared to the other unknown parent’s side? i.e. 9500 on one side; 4300 on the other (split by parent in Ancestry)?

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