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Half-Sister or Half-Aunt

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  • Half-Sister or Half-Aunt

    Hello, I am an adoptee who located biological mother information via testing on FTDNA. Biological mother had passed unexpectedly years before and her other children, all half-siblings to me (2 older and 4 younger) did not know anything about the circumstances surrounding my adoption or any clue about the biological father - she had told them about me but did not share details - they were teenagers when she told them- and it didn't occur to them to ask for details as they got older (they are all adults now).

    Much to my surprise, shock really, a match appeared on FTDNA within the last few weeks showing the half-sister/aunt, niece, grandmother-granddaughter relationship range. I have done significant research on the individual who matches and she is 5 years older than I am so it seems that the half-sister/aunt would be the only relationship match option.

    The match is on the biological father's side because there are zero dna matches on my biological mother's side with her dna/family tree. This woman's siblings would have been too young to be my biological mother. However, she does have a half-brother (same mother different father) that would have been old enough to possibly be my biological father.

    From what I understand in researching if this woman was my half-aunt she would likely show up as a first cousin relationship because she was not a full sibling to the male. Is this correct or am I all wet in my understanding?

    My shared cM with her is 1906 and the X-Match on the FTDNA Chromosome browser is almost identical.

    It does not appear anyone else from her immediate family has tested on FTDNA. I have not contacted her because of the potential disruption it could cause her (note: both her parents are deceased). Finally, I have my family finder level matching set at "None" so she has likely not seen this match. I am trying to determine, as best as possible, if this would be a half-aunt or half-sister based on the limited information available.


  • #2
    My shared cM with her is 1906 and the X-Match on the FTDNA Chromosome browser is almost identical.

    It's possible for women to share an entire X-chromosome with a maternal or paternal aunt.

    Half-sister who have the same father will both receive their father's only X-chromosome.

    I think she is likely to be your half-sister.


    • #3
      Here is a free tool that is handy for visualizing these relationships.

      Most likely she is a half sister.


      • #4
        Thank You-

        For the responses and information. Very helpful...

        I was leaning toward half-sister as well (after sitting on half-aunt for a few days until I really worked it through and thought it was more likely half-sister).

        This "adopted" stuff can be a real rollercoaster at times. Sigh.. but at this point in all the many years of searching for answers, I am somewhat accustomed to the gut punches... and ups and downs... :0)

        Thanks again- appreciate the time you took to reply.


        • #5
          I'd say definitely half-sisters based on your matching one of your X-chromosomes nearly in its entirety. That would confirm that you have the same father (or that your fathers were identical twins).


          • #6
            Thanks Dabney-

            The identical twins for the fathers is an interesting thought and maybe worth me exploring if I can determine if her father had an identical twin. I say this because I cannot track how her father and my biological mother would have encountered each other, knowing what I do of my years of research on her whereabouts during her life and my discussions with my biological mother's other children.

            That being said, without the ability to speak to my biological mother directly there are undoubtedly gaps of information no one but she could tell me.

            Appreciate the information-