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Possible half sister what test to take

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  • Possible half sister what test to take

    Would the Family Finder test be the best test to determine half siblings.The reason I am asking is that I wasn't told who my real father was until I was sixteen.My parents were both separated and only living together at the time of his death so were not married when I was born . I was giving my mother's x husband last name .I took the Ydna 111 test and a match with my real father's family name by 5 marks off at 111 markers.I have over 20 match in the 37 to 67 markers range and all have the same last name.The woman that I want to test is his last living daughter and she has agree to take the dna test.Is FF the right test for her to take.Any help would be appreciated.

  • #2
    Yes, FF is the right test. For a half sibling you would typically match on between 20-30% of your DNA. It will be very unambiguous.

    In my experience FF and similar tests from other companies is accurate relationship wise out to the second or third cousin range. Beyond that things get iffy as to distance as recombination variance leads to all sorts of weirdness. I have a third cousin once removed that I share more DNA with than my Uncle who is a third cousin to that person.

    For half siblings though it is very accurate.


    • #3
      I think we will all concur that FF [autosomal] is the best. It is also the only 'hobby grade' test that will tell you anything regarding this particular situation. You say you have different mothers and x- and mt- will tell you nothing, and she has no y- .

      FF, though none of us doubts its accuracy, would likely not hold up in court which is why I say 'hobby grade'.



      • #4
        Hi 1_mke and hansonrf thank you for your help and replies.hansonrf I am not looking for anything to hold up in court this is for my records only.I know who my father was as like I said my mother told me when I was sixteen .This information is for my grandchildren and my great-grand child.If the test comes back that she is my half sister then I have it in dna proof for their records.


        • #5
          In terms of cMs, what would half siblings be expected to share - around 1800 cMs?


          • #6
            I think that's right; Full siblings 2700 on average, half sibs ~1800.

            Bob H


            • #7
              Originally posted by marietta View Post
              In terms of cMs, what would half siblings be expected to share - around 1800 cMs?
              Hi ,I am new in this but it sound like hansnof is right as I match my half sister that we have the same mother for a Total CentiMorgans (cM): 1820.06733
              Shared DNA Segments: 58 and matches me on chormosome X from position 23098594 to 154570039 for a total of 151.8cM.


              • #8
                Half sibling matches vary just like any others. I've seen one just south of 1900 cM's for instance. This is why people generally talk in terms of ranges.

                20-30% is going to hit the vast majority of the bell curve but theoretically it could be anything from 0-50%.