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Help Please - Proving Paternal 3rd Cousins

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  • Help Please - Proving Paternal 3rd Cousins

    Hi,

    Thanks for reading this. I need your help.

    Here is the situation. Two men who appear to be direct paternal third cousins on paper (common great great grandparents on the direct male line according to parents names given at marriage and death).

    However, the Y-37 came back with 2 markers off. The Y-67 came back also with 2 markers off. From a previous post someone said they had the experience of having two first cousins be 4 markers off on Y-37 so it sounds reasonable that although these guys are 2 markers off, they might still be third cousins?

    What would you suggest would be the next step in solving the mystery?

    Would a Y-111 be useful at all? (one man is already tested at Y-111)

    Would a Family Finder test be definitive proof assuming it comes back showing that they share autosomal DNA?

    Please comment!

    Thanks!!!!

  • #2
    Originally posted by SparkyMc View Post
    ...so it sounds reasonable that although these guys are 2 markers off, they might still be third cousins?
    Yes, definitely reasonable.

    Originally posted by SparkyMc View Post
    Would a Y-111 be useful at all? (one man is already tested at Y-111)
    Not really, since you can't prove the precise relationship with Y-DNA alone, no matter how many markers you compare. The best you can do with Y-DNA is what you've already done, which is finding a very close match and therefore proving that they share a direct paternal line.

    Originally posted by SparkyMc View Post
    Would a Family Finder test be definitive proof assuming it comes back showing that they share autosomal DNA?
    Family Finder gives estimated relationship ranges, so they should get "2nd to 3rd cousin" or "2nd to 4th cousin" or "3rd to 5th cousin" as the estimate. Similar to the situation with Y-DNA, this will indicate that they are indeed closely related, but it won't prove that the exact relationship is 3rd cousin.

    That said, please be aware that it's also possible that they could get a slightly closer or more distant estimate, even if they are indeed true 3rd cousins.

    There's even a possibility that they won't show as matches at all, since about 10% of true 3rd cousins actually don't inherit enough of the same autosomal DNA from the common ancestors to show as a match.

    So...

    A match on FF adds support to the paper trail, but doesn't prove the precise relationship.

    A lack of match on FF won't necessarily refute the paper trail -- as mentioned above, in 10% of cases, true 3rd cousins simply don't share enough autosomal DNA to show as matches.

    Originally posted by SparkyMc View Post
    What would you suggest would be the next step in solving the mystery?
    I think the only absolute PROOF of the precise 3rd cousin relationship can come from the paper trail. Y-DNA and FF matches will add strong support to the paper trail.

    Elise
    Last edited by efgen; 3 July 2014, 04:09 PM.

    Comment


    • #3
      Originally posted by efgen View Post
      Yes, definitely reasonable.
      Not really, since you can't prove the precise relationship with Y-DNA alone, no matter how many markers you compare. The best you can do with Y-DNA is what you've already done, which is finding a very close match and therefore proving that they share a direct paternal line.
      Are you saying that Y-111 does not offer any further insight than Y-67?

      Why not?

      What do matches on Y-111 mean then?


      I have seen a case where a man was 4 markers off on Y-67 and was not a match at Y-111. What does that mean?

      Comment


      • #4
        And PS. I guess I should rephrase. I am trying to prove that their common paternal ancestor was more recent and not a good deal farther back. If they had an exact match on all markers that would be awesome but alas, they don't.

        The paper evidence is limited to the marriage certificate of each ancestor listing the same father and mother.

        In Family #2 no parents were listed on the death certificate of the ancestor.

        We do not have birth / baptism for either ancestor nor do we have census records for them prior adulthood when they are already head of their own households.

        So no concrete proof really right?

        Comment


        • #5
          Originally posted by SparkyMc View Post
          Are you saying that Y-111 does not offer any further insight than Y-67? Why not?
          What do matches on Y-111 mean then?
          Well, it will give you further confirmation that it's a close match. GD=2 on 111 markers is stronger than GD=2 on 67 markers. But you still can only call it supporting evidence, not PROOF, of the 3rd cousin relationship.

          Originally posted by SparkyMc View Post
          I have seen a case where a man was 4 markers off on Y-67 and was not a match at Y-111. What does that mean?
          Hmm, I'd have to see this one. The match threshold for 111 markers in myFTDNA is GD=10. So it seeems unlikely to me that someone who has only 4 differences on the first 67 markers would end up with 7+ more differences on markers 68-111.

          Elise

          Comment


          • #6
            Originally posted by efgen View Post
            Hmm, I'd have to see this one. The match threshold for 111 markers in myFTDNA is GD=10. So it seeems unlikely to me that someone who has only 4 differences on the first 67 markers would end up with 7+ more differences on markers 68-111.

            Elise
            It was kinda disappointing How do I "show" it to you?

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            • #7
              PS.

              The second case I was talking about. Here is a screenshot for Elise.

              The person in question is Michael. Exact match at Y-37, off by 4 markers at Y-67, then no match at Y-111.
              Attached Files
              Last edited by SparkyMc; 3 July 2014, 05:10 PM. Reason: further info

              Comment


              • #8
                Originally posted by efgen View Post
                So it seeems unlikely to me that someone who has only 4 differences on the first 67 markers would end up with 7+ more differences on markers 68-111.
                I think this can happen if one lineage has a Null (0) at one of the 68-111 markers.

                Comment


                • #9
                  Originally posted by lgmayka View Post
                  I think this can happen if one lineage has a Null (0) at one of the 68-111 markers.
                  Yep, that's what I'm thinking -- or some other multi-step mutation that caused the GD to go out of range.

                  SparkyMc, if you want to send me the kit number so I can look up the match, I'll be glad to check into that particular case. I sent you a PM about this, just mentioning it here too in case you didn't see the PM.

                  Elise

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                  • #10
                    Thanks a million.

                    Sent a PM with Kit #.

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                    • #11
                      Re: "Two men who appear to be direct paternal third cousins on paper (common great great grandparents on the direct male line according to parents names given at marriage and death)." --

                      Would definitely recommend doing the Family Finder test on both.

                      Also - is the father of either (or both) alive? If not - does either (or both) have an aunt or uncle on their father's side still alive?
                      What other relatives of either are alive?

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