Proving or Disproving a Half Sibling Relationship Using DNAPainter

I had this nagging match at MyHeritage for some time who had not responded to messages and who didn’t have a tree. When she did reply, she explained that she was adopted, but I had already been working on how she was related.

Initially, I didn’t think too much of the match, especially when she didn’t reply, but after SmartMatching and Triangulation appeared on the scene, this match haunted me just about daily. Who the heck was Dee? We share enough DNA that we might even share a family resemblance.

Recently, when I became focused on my Dad’s life and (ahem) bad-boy mis-adventures once again, I realized that while this clearly isn’t a half-sibling match, my half-sibling would likely be long-deceased. I was born late in my father’s life and he was breaking hearts 40 years earlier – which means he could also have been fathering children. Dee could be my half-sibling’s child or grandchild.

Let’s take a look at this situation and how I used DNAPainter to quickly narrow the possibilities, even with no additional information.

The Problem

Here’s my match to Dee (not her name) at MyHeritage.

Dee matches me at 521 cM on 17 segments.

Taking a quick look at the DNAPainter Shared cM Tool, you can see that Dee falls into the non-dimmed relationship ranges below, with dark grey being the most probable.

The most likely relationships are shown in the table below.

Dee is in her 50s, so she’s clearly not my great aunt or uncle or grandparent.

The Possibilities

Based on who she matches, I know the match is from my father’s side. I have no full siblings and my mother’s DNA is at MyHeritage.

My father could have been begetting children beginning about 1917 or so and could have continued through his death in 1963.

My half sister’s daughter has also tested at MyHeritage, and Dee matches her more distantly than me, so Dee is not an unknown descendant of my half-sister.

Dee could have been a child or grandchild of a half sibling that I’m unaware of – which of course is my burning question.

I checked the in-common-with matches and while they made sense, I needed something much faster than working with multiple trees and matches and attempting to build them out.

Besides, I desperately wanted a quick answer.

DNAPainter to the Rescue

I’ve written three previous articles about utilizing DNAPainter.

I continue to paint matches where I can identify known ancestors. Currently, I’m up to 689 segments identified and painted which is about 62% of my genome.

Surely this investment should pay off now, if I can only figure out how.

I’ve painted hundreds of segments on both my paternal grandmother and grandfather’s sides. If Dee is a half sibling (descendant) to me, she will match both my paternal grandmother’s line and my paternal grandfather’s line. If Dee is related on one of those lines, but not the other, then Dee will match one grandparent’s line, but not the other grandparent’s line.

Dee can’t be descended from a half sibling if she doesn’t match both of my paternal grandparents, meaning William George Estes and Ollie Bolton’s lines.


The first thing I did was to paint the segments where Dee and I match, assigning a unique color.

After painting, I compared each chromosome individually, looking at the other ancestors painted that overlapped with the bright yellow.

The next step was to look at each chromosome and see which ancestor’s DNA overlaps with Dee’s.

Without fail, every single one of these segments matched with my paternal grandfather’s side, and none matched with my paternal grandmother’s side.

To confirm, I have a cousin, we’ll call him Buzz, whose ancestor was my grandmother’s brother, so Buzz is my second cousin. If Dee is my half sibling’s child or grandchild, Buzz, who also tested at MyHeritage, would be Dee’s second cousin or second cousin once removed. No second cousins have ever been proven NOT to match, so it’s extremely unlikely that Dee is descended through Ollie Bolton.

Is there a very small possibility? Yes, if Dee is actually a second cousin twice removed from Buzz, which is genetically the equivalent of a third cousin. Third cousins only match about 90% of the time.

However, Dee also doesn’t match anyone else on my grandmother’s side, so it’s very unlikely that Dee descends from Ollie Bolton’s parents, Joseph “Dode” Bolton and Margaret Clarkson/Claxton.

Therefore, we’ve just “proven,” as best we can, that Dee does NOT descend from a previously unknown half-sibling.

We’ll just pause for a minute here – I was so hopeful☹

Regroup – Other Possible Relationships

OK, redraw the chart without Ollie. Dee is still very closely related, so what are the other possibilities?

Dee does match people with ancestors from both the lines of Lazarus Estes and Elizabeth Vannoy, so Dee is either an unknown descendant of William George Estes or his parents, given how closely she matches me and other descendants of this family.

Or… as luck would have it, Dee could also be descended from the sister of Lazarus Estes (Elizabeth Estes) who married the bother of Elizabeth Vannoy (William George Vannoy.) Yes, siblings married siblings. Two children of Joel Vannoy and Phoebe Crumley married two children of John Y. Estes and Rutha (or Ruthy) Dodson.

You know, these mysteries can never be simple, can they?

In the chart above, gold represents the people who descend from a combination of a pink and blue couple. Joel Vannoy and Phoebe Crumley are shown twice because there was no easy way to display this couple.

One way or another Dee and I are related through these two couples. Of course, I’m curious as to how, and excited to help Dee learn about her family, but this isn’t going to be an easy solve, because of the potential double descent. Under normal circumstances, meaning NOT doubly related, Dee is most likely my half-great niece, meaning that her unknown grandparent is either a child of William George Estes (my grandfather) or descended from his parents, Lazarus Estes and Elizabeth Vannoy.

However, the doubling of DNA in the William George Vannoy/Elizabeth Estes line would make Dee look a generation closer if she descends from that line, so the genetic equivalent of descending from Lazarus Estes and Elizabeth Vannoy. The only way to solve for this equation would be to see how closely she matches a descendant of Elizabeth Estes and William George Vannoy – and no one from that line is known to have tested today.

For now, my driving question of whether I had discovered an unknown half-sibling has (most probably) been answered between the segment information at MyHeritage combined with the functionality of DNAPainter.

14 thoughts on “Proving or Disproving a Half Sibling Relationship Using DNAPainter

  1. HI, i hope I get a reply on this. If you can figure out how you are related to someone who is on your Dad’s side but not your mother’s side, why can’t I see what I’ve inherited from my father? I finally got someone at Ancestry to cough up the fact that I CAN get a whole “readout” or whatever it’s called but they can’t tell me which parents contributed what.

    • To do this technique, you have to know which side the match is on. Furthermore, ancestry does not provide segment info so you’ll have to use either Family Tree DNA or MyHeritage or 23andMe who do.

  2. I have a similar situation trying to determine a match on my father in law’s side. His grandfather was adopted and I have been trying to find matches on that side of the family to hopefully determine who his grandfather’s parents were. A match to my father in law at 219 cMs and to his brother at 310 cMs is thus far the only relatively close match on that side. Turns out, the match is also adopted and was born in the city their grandfather moved to in his early 20s- not the city he was born and raised in. This, combined with her age- she’s almost 50 (around the same age as my FIL’s youngest brother), makes me suspect she may be the daughter of FIL’s half aunt/uncle, that no one knew about… 1/2 First Cousin 1R. DNA Painter suggests that is certainly in the realm of possibility. She is waiting on her birth certificate as her state has opened adoption records. Hoping that may reveal new details…. in the meantime, hoping for more close matches!

  3. Roberta, I was able to find my unknown grandfather using a similar technique. My match was at 23andMe and unresponsive. I entered her details into DNAPainter and waited until a new match popped up at MyHeritage that overlapped the first. Then, through diligent tree building, I discovered the two were aunt and niece. Fortunately, the second match did reply, and I was able to find the connection. Everything fell into place when I also found matches to the new grandfather’s maternal side, primarily as a result of tree building for ICW matches. Now busy researching a whole new branch of my tree:-).

  4. Roberta, at MyHeritage, when we are given the TGs, has the software actually done a one-to-one comparison to determine this , or are these TGs that are given to us, just ICWs?

    Many thanks!

  5. A cousin of mine is working a case like this and she allowed me to pack around with her on this adventure. You have given me something to use and might could help solving the mystery.

  6. Roberta! “Surely this investment should pay off now, if I can only figure out how.”
    And this is a recent post of yours! I’m surprised!!!! I definitely want an update on progress with painting payoffs, so I can finally put my spreadsheets and hours of compiling sorting comparing contrasting into something better than I have so far! 🙂

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