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Which side of the family?

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  • Which side of the family?

    Hi, all!

    I have an autosomal match, estimated as a 3rd - 5th cousin, who has a line in his family tree that matches with my maternal line. But this match is not a match to my mother. This match has a small, but genealogically insignificant, match with my brother - does not show up in FTDNA as a match to my brother, and is not considered a match in

    Would I be wasting time pursuing trying to tie this match to a family line on my maternal side, if he is not a match to my mother? Or could there be some dna fluke that would make it possible for this person to match on my maternal line, without being a match to my mother.

    Here's the matrix from
    Me Mother Brother Match
    Me 3578.6 2917.1 21.1
    Mother 3578.6 3585.3
    Brother 2917.1 3585.3 6.7
    Match 21.1 6.7

    Thank you for any insight!


  • #2
    Don't waste your time!

    a 21.1cm match would be ancient and about as distant as they come.


    • #3
      Originally posted by JDP1144 View Post
      a 21.1cm match would be ancient and about as distant as they come.
      I would disagree with that. I've tested 5 family members and we have very few matches who share over 20 cM. If I ignored matches under 20 cM, I wouldn't have anything to work with at all. I think it's because my only ancestor with colonial American ancestry was born about 1872 and few people in the European countries where my other ancestors lived have tested. But I'm searching for colonial American ancestors. The closest of the unknown ones were born about 1810.

      So I think what you work with depends on the situation. If you're looking for really close relatives you need much longer segments.

      Last week I had an adoptee contact me, insisting that someone in my family had to know who her parents were. She shared only 11 cM with my father and nothing at all with my double cousins. I had a hard time convincing her (if I ever did) that that tiny segment of DNA indicated a common ancestor who lived hundreds of years ago, and that no one in my family would know who her parents were.


      • #4
        Match on maternal line that isn't match to mother? Possible?

        Thanks for your replies!

        FTDNA estimates the relationship as 3rd - 5th cousin, and as I recall gave it a generational distance of something like 4.7, so I feel that determining the MRCA is potentially achievable.

        The thing is, the match shows in their paper tree a line that I know connects with my maternal line - no doubt about it. And it's the family line that interests me the most, so that's why I want to pursue it.

        But this match is not a common match with my mother. What I really want to know is whether it is possible to have a maternal match that doesn't match my mother. It seems to me that it's not possible - I can't inherit any maternal dna that my mother doesn't also have. But I also wonder if there's some kind of fluke or inaccuracy or something.

        I don't really understand why this match doesn't show as a common match with my mother, because the match shares 15.45 cM with me on Chromo 12 with a start of 107280282 and end of 116957437. On Chromo 12 my mother is a start of 61880 and end of 132287718, so it seems like my mother overlaps with the match, yet isn't reflected as a match - on and on FTDNA.

        I'll be appreciative of any insight!

        Thanks, again, for taking time to respond!



        • #5
          Mary, have you done a one-to-one with your mother and the match at Gedmatch? Be sure to lower the cMs threshold to ~2cMs to pick up everything. Maybe they match, but at a lower threshold; the random nature of DNA, and all that. And, yes, I know, if you match the person on your mother's side, she should show at least as many cMs to the match as you (and in this case, the dna would not have re-combined, but passed down intact to you).

          Sometimes when I know I should be matching a certain surname, but do not, I lower the threshold, and lo and behold, they are there; and that tells me a little something.

          But it still looks like you are matching this person on your father's side.

          But, could it just be that the matching algorithms are not picking up the match between your mother and the match? That sounds like a more credible answer.
          Last edited by Biblioteque; 14 February 2016, 06:42 PM. Reason: add


          • #6
            As marietta states, run the one to one against your mother and this match.

            The 21cM displayed in matrix is the total DNA you share with this match, not the longest segment length. If you run the one to one against your self and this match also, you will probably see some of the same segments that your mother shares with this match.


            • #7
              @prairieland - At Gedmatch, should she do a one-to-one on the X to see if her mother shares with the match there? Or do the geneticists still say in order to have an X match you have to first have an autosomal match? And, if so, what cMs threshold on the X would they use, since the threshold on the X is lower than autosomal, and different according to gender? There does not seem to be a consensus of opinion on the dynamics of the X yet.
              Last edited by Biblioteque; 14 February 2016, 11:13 PM. Reason: add