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  • A hypothetical question - need thoughts

    Person A and Person B are female.
    Person A and Person B are half-siblings, sharing the same father.
    Person A and Person B both take Autosomal DNA tests.
    Comparison of raw DNA files through GEDMATCH show no shared DNA.
    Ancestry.com shows no DNA relationship between the two people.

    Are Person A and Person B truly related?

  • #2
    If a comparison was done using Family Finder here at Family Tree DNA, the answer would be very simple: 100% sure that they do not have any common genetic parent or grandparent.

    I do not know whether Ancestry.com or GEDMATCH have any flaws that might make them to not show shared DNA, if there is a significant or detectable amount of it (like when sharing at least one parent or grandparent).

    However, it has happened on rare occasions that the same Family Finder data was loaded into two different kits. An obvious mistake. Easy to spot, both kits would suddenly show parent/child relationship. Please ask FTDNA Support to independently verify both kits.

    W. (Mr.)

    P.S.
    I would recommend that you download both Family Finder (or from wherever they originated) raw files to your home computer, and then performed a comparison on your home computer.

    Would you know how to open a file with results and check the number of no calls? If not, I hope somebody has a handy cheat sheet they are willing to share.

    From the Family Tree DNA Learning Center:
    http://www.familytreedna.com/learn/a...raw-data-file/
    How do I read my Family Finder raw data file?

    Comment


    • #3
      Originally posted by springermom View Post
      Person A and Person B are female.
      Person A and Person B are half-siblings, sharing the same father.
      Person A and Person B both take Autosomal DNA tests.
      Comparison of raw DNA files through GEDMATCH show no shared DNA.
      Ancestry.com shows no DNA relationship between the two people.

      Are Person A and Person B truly related?
      From the information you have provided I assume neither have tested at FTDNA, not that it matters where they tested.

      My wife, daughter and I all tested at 23andMe before FTDNA announced FF. Our daughter is shown as a daughter. GEDmatch show a high level of matching.

      Based on the information you provided I don't believe they share a common ancestor.

      Comment


      • #4
        Originally posted by springermom View Post
        Person A and Person B are female.
        Person A and Person B are half-siblings, sharing the same father.
        Person A and Person B both take Autosomal DNA tests.
        Comparison of raw DNA files through GEDMATCH show no shared DNA.
        Ancestry.com shows no DNA relationship between the two people.

        Are Person A and Person B truly related?
        No, it would be 100% that they don't share a parent in common.

        Comment


        • #5
          I would agree that they are not related.
          Half sisters that share the same father would also match along the entire X chromosome, each would have received fathers full X.

          Comment


          • #6
            Thank you. It looks that way to me, but I wanted to make certain that there was no trick to it.

            Comment

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