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The GEDmatch Relationship Tree tool - Wed, 24 Jan 2018

I hadn’t tried this one before. Have you?

image

It’s a Tier 1 tool, so you have to pay GEDmatch the $10 a month to use it.

What an imaginative innovative idea. They’re using expected autosomal sharing and expected X sharing between two people to determine relationships and they show a tree for the two people. When I run myself against one of my closest X matches on GEDmatch (28 cM shared X, 42 cM shared autosomal) who I have no idea how I’m related to, after increasing the overlap from 1 (which gave no results) to 2, I get this:

image

What it tells me, is that using rules of how autosomal DNA and X-DNA is passed from parent of a given sex and child of a given sex, my shared amounts with this person most closely match the estimates for two relationships (as shown in the chart above). This person is most likely my 3rd cousin in one of these two ways:

  1. My mother’s father’s mother’s sister’s son’s daughter’s daughter.

  2. My mother’s father’s mothers’ sister’s daughter’s son’s daughter.

This doesn’t preclude other ways that we could be related. I could increase the overlap to 3 and get more possibilities. But it does give some insight as to what the relationship might be.

At GEDmatch they say this tool is experimental. It’s been around a few years and there is very little documentation about it. The best writeup I’ve seen is one by Israel Pickholtz in 2014.

How does it work?

Well that exact question was asked on my favorite Genealogy and Family History Question and Answer Site, and you can see my answer there.

Does the tool help? Well. I’m going to email that person, and ask her if her who her mother’s father’s mother and her father’s mother’s mother were and where they were from and see if they can connect to my mother’s father’s mother.

With regards to using relationship techniques like this in genealogy software like Behold or DNA analysis tools such as Double Match Triangulator, I have some ideas. Stay tuned.

—-

Update Jan 25:  I contacted the person administering the account who was an APG member administering lots of DNA kits. He pointed out that I didn’t read the instructions correctly and entered the wrong values. It wanted autosomal and X values from the 1 to 1 tool and I used the values from the one-to-many tool. He also said the person I matched to was likely a generation different from me. That doesn’t affect anything I say in the post about the tool, but only means it is using example input.

So I entered the correct values into the Relationship Tree tool and it now gave a single result, not too much different than what is in the diagram above. At 3rd cousins once removed, the line we might be related to is at least one generation further than either of us have been able to genealogically research.

None-the-less, try the tool. It may help you if both you and your match have genealogically researched enough generations back on the possible connecting lines.

4 Comments           comments Leave a Comment

1. jbissett (jbissett)
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Joined: Thu, 12 Jan 2017
10 blog comments, 0 forum posts
Posted: Thu, 25 Jan 2018  Permalink

Hi Louis, Once again you have provided a most valuable explanation of an existing GedMatch feature that so far I had not understood or used.
My maternal half-brother only shows 2 X-dna matches for unknown cousins. I ran the first one (only 8.2 cms atDna and 7.5 cms X-Dna) and I am pleasantly surprised to find that it leads back to my mother’s father’s mother’s father, which although I have a huge number of matches for my maternal line, I have so far been unable to take a Dna match back to our maternal gggf. Of course, all this has done (as with most genealogy questions when solved) is to cause me a lot more research work to follow the two sons’ lines back down to the present.
If my research confirms this DNA trail, I will post another comment, because this will be extremely valuable.

2. Louis Kessler (lkessler)
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Joined: Sun, 9 Mar 2003
237 blog comments, 226 forum posts
Posted: Thu, 25 Jan 2018  Permalink

Joe: We’re just beginning see the development of good tools to analyze all this DNA stuff. GEDmach is doing a great job providing new ideas like this, and it’s great when there’s one that can help us make sense out this nonsense.

3. jbissett (jbissett)
United States flag
Joined: Thu, 12 Jan 2017
10 blog comments, 0 forum posts
Posted: Fri, 26 Jan 2018  Permalink

Louis: Do you have a moment to help me understand a few issues with the relationship tree?

4. Louis Kessler (lkessler)
Canada flag
Joined: Sun, 9 Mar 2003
237 blog comments, 226 forum posts
Posted: Fri, 26 Jan 2018  Permalink

Joe: Send me an email.

 

The Following 2 Sites Have Linked Here

  1. This week’s crème de la crème — January 27, 2018 | Genealogy à la carte : Sat, 27 Jan 2018
    [...] The GEDmatch Relationship Tree tool by Louis Kessler on Behold Genealogy. [...]

  2. Flipping Through Records » Friday’s Five at Five for February 23, 2018 : Fri, 23 Feb 2018
    [...] looking forward to trying out the The GEDmatch Relationship Tree tool mentioned by Louis Kessler. I have a client searching for a birth grandfather and his DNA matches [...]

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