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  • Relationship Possibilities

    First post

    I’m going to try to explain this correctly.

    My 15 year old daughter (I’m her father) did an Ancestry DNA kit.

    It showed she has two close relatives ( first to second cousin range). The second person on the list is my half sister by my father. My daughter shares 786 cMs across 19 DNA segments with my half sister, my daughter’s half-aunt.

    The first person on the list is not know by anyone on either side of the family ( mine or you wife’s)

    My daughter shares 822 cMs across 31 DNA segments with him. By viewing shared matches, I’m able to see that he is related to my mother’s side of the family and not anyone from my wife’s side of the family.

    I contacted the individual through the message board, and he told me that was born 8 years after me in my hometown where my mother (who was single at the time),as well as her two younger brothers lived at the time. All three of these siblings were in their 20s at the time. He was adopted immediately, and his records are sealed.

    I’m guessing he is my first cousin from one of my uncles or somehow my mother had a child and concealed it from me when I was eight years old.

    Could I be missing something?

  • #2
    Originally posted by Cosmic Rocker View Post
    First post [----]
    Welcome to the world of genetic genealogy!

    Originally posted by Cosmic Rocker View Post
    [----] Could I be missing something?
    Yes! Please test yourself.


    Mr. W.

    P.S.
    Some participants here are very good in interpreting the results, so I will leave the interpretation of your results to them. But, I just want to confirm something, did you look atAnd I highly recommend that you test yourself regardless of the interpretation you receive.

    Comment


    • #3
      I am testing myself. One of my first cousins is as well.

      Comment


      • #4
        Originally posted by Cosmic Rocker View Post
        I am testing myself. One of my first cousins is as well.
        Update. My first cousin was tested and shares 817 cMs with the mystery person (and 605) with me.

        I was tested and share 1259 with mystery person.

        It appears we are all first cousins.

        Any other possibilities? Is it possible he is my half-brother?

        Comment


        • #5
          Originally posted by Cosmic Rocker View Post
          Update. My first cousin was tested and shares 817 cMs with the mystery person (and 605) with me.

          I was tested and share 1259 with mystery person.

          It appears we are all first cousins.

          Any other possibilities? Is it possible he is my half-brother?
          Looks like both you and the mystery person need to upload your kits to GEDmatch and do a 'one-to-one' for your X-chromosomes. Males get only one X-chromosome and that would be from the mother. The X passed by the mother to the child would have parts of each of her two X-chromosomes and children would normally get different combinations. If you two are half siblings by the same mother, you would have a pretty sizable X-DNA match.

          Good luck!

          Jack Wyatt

          Comment


          • #6
            Are you able to test your mother or one of her siblings?
            Is there another cousin you can test from another of you mothers siblings line (different siblings line then the cousin you have tested)

            Do you know if this match has done yDNA testing? If so ask him what his surname matches are?

            If you are able to test your mothers yDNA line (male 1st cousin of your mothers brothers lines) and this match does yDNA testing, it will show if he is likely to be a son of one of your uncles if yDNA matches

            Comment


            • #7
              In regards to X, if he shares XDNA with you of an adequate longest segment size (greater then 10cM), he could possibly be a maternal half sibling (very low end of scale for cM total to be half sibling), or he could be a son of your mothers sister (if she has one).
              There is no male to male transmission of XDNA, so if he shares XDNA with you, you can definitely rule out any of your mothers brothers.

              https://dnapainter.com/tools/sharedcmv4/1259

              Comment


              • #8
                Thanks everybody for the suggestions.

                Comment


                • #9
                  Originally posted by prairielad View Post
                  In regards to X, if he shares XDNA with you of an adequate longest segment size (greater then 10cM), he could possibly be a maternal half sibling (very low end of scale for cM total to be half sibling), or he could be a son of your mothers sister (if she has one).
                  There is no male to male transmission of XDNA, so if he shares XDNA with you, you can definitely rule out any of your mothers brothers.

                  https://dnapainter.com/tools/sharedcmv4/1259
                  The dns painter shows a 70 percent chance of us being 1st cousins, 30 percent half chance of being half brothers.

                  Incongruously, it shows my daughter and him as 95 percent half-uncle/half niece and only 5 percent of being 1st cousin once removed which is what the two of them would be if he is my first cousin.

                  An additional data point is that it shows my known first cousin and I as only having a 24 % chance of being first cousins and my daughter and my first cousin as only a 31% chance of being the correct relationship (1C1R)

                  Will definitely look at gedmatch.

                  Comment


                  • #10
                    Originally posted by Cosmic Rocker View Post
                    The dns painter shows a 70 percent chance of us being 1st cousins, 30 percent half chance of being half brothers.

                    Incongruously, it shows my daughter and him as 95 percent half-uncle/half niece and only 5 percent of being 1st cousin once removed which is what the two of them would be if he is my first cousin.

                    An additional data point is that it shows my known first cousin and I as only having a 24 % chance of being first cousins and my daughter and my first cousin as only a 31% chance of being the correct relationship (1C1R)

                    Will definitely look at gedmatch.
                    If you share more cMs with that Mystery person than your daughter, then do not look at her matching the Mystery person!

                    Unless you have reasons to believe that Mystery person is related to your daughter both through you and her mother. However, given the numbers you had shared with us, even if it is so, that would be a secondary investigation - after you confirm your relationship.


                    Mr. W.

                    Comment


                    • #11
                      Originally posted by dna View Post
                      If you share more cMs with that Mystery person than your daughter, then do not look at her matching the Mystery person!

                      Unless you have reasons to believe that Mystery person is related to your daughter both through you and her mother. However, given the numbers you had shared with us, even if it is so, that would be a secondary investigation - after you confirm your relationship.


                      Mr. W.
                      He is only related to my daughter through me.

                      Are you saying it is irrelevant how many cMs my daughter shares with him?

                      Comment


                      • #12
                        Please be careful with X:

                        Someone wrote: "If you two are half siblings by the same mother, you would have a pretty sizable X-DNA match."

                        Not necessarily. You could share nothing in a rare but possible case: each one inheriting a different X. Mother has two X chromosomes.

                        -----------
                        Someone else wrote: "There is no male to male transmission of XDNA, so if he shares XDNA with you, you can definitely rule out any of your mothers brothers."

                        My relative shares a 30cM segment of X with someone on gedmatch. No common ancestor in sight, and also no autosomal match. Also, a number of X-matches share about 20cM on X and nothing else.
                        It is possible that the Mystery's father is one of your uncles, and his mother is such a distant match on X.
                        -----------

                        Another testing option is mtDNA test for you and Mystery person (costs more money):

                        mtDNA is inherited from the mother.
                        What to do with the mtDNA result?

                        a) Your results are different.
                        Two people with different mtDNA haplogroup do not share the same mother.

                        b) Your results are identical.
                        Two maternal half siblings have the same mtDNA.
                        (If you share a very common type of mtDNA, it can be a coincidence, sharing a great-great-......-greatgrandmother a long time ago. Unlikely scenario in this case.)

                        Wait, and what if ...
                        -----------
                        What if???
                        Where were your maternal grandparents at the time?
                        Can you exclude them 100%?
                        Could your Mystery man be your half-uncle?
                        DNApainter https://dnapainter.com/tools/sharedcm says:
                        Half Aunt/Uncle
                        891 (500 – 1446)

                        Was your grandmother young enough to have another child? (If she is the bio-mother, you and Mystery would also share mtDNA)
                        What about grandfather? (If he is the bio-father, your male cousins from your uncles would share Y with Mystery)

                        Instead of answers, more questions to be answered...

                        Comment


                        • #13
                          Originally posted by Emona View Post
                          Please be careful with X:

                          Someone wrote: "If you two are half siblings by the same mother, you would have a pretty sizable X-DNA match."

                          Not necessarily. You could share nothing in a rare but possible case: each one inheriting a different X. Mother has two X chromosomes.

                          -----------
                          Someone else wrote: "There is no male to male transmission of XDNA, so if he shares XDNA with you, you can definitely rule out any of your mothers brothers."

                          My relative shares a 30cM segment of X with someone on gedmatch. No common ancestor in sight, and also no autosomal match. Also, a number of X-matches share about 20cM on X and nothing else.
                          It is possible that the Mystery's father is one of your uncles, and his mother is such a distant match on X.
                          -----------

                          Another testing option is mtDNA test for you and Mystery person (costs more money):

                          mtDNA is inherited from the mother.
                          What to do with the mtDNA result?

                          a) Your results are different.
                          Two people with different mtDNA haplogroup do not share the same mother.

                          b) Your results are identical.
                          Two maternal half siblings have the same mtDNA.
                          (If you share a very common type of mtDNA, it can be a coincidence, sharing a great-great-......-greatgrandmother a long time ago. Unlikely scenario in this case.)

                          Wait, and what if ...
                          -----------
                          What if???
                          Where were your maternal grandparents at the time?
                          Can you exclude them 100%?
                          Could your Mystery man be your half-uncle?
                          DNApainter https://dnapainter.com/tools/sharedcm says:
                          Half Aunt/Uncle
                          891 (500 – 1446)

                          Was your grandmother young enough to have another child? (If she is the bio-mother, you and Mystery would also share mtDNA)
                          What about grandfather? (If he is the bio-father, your male cousins from your uncles would share Y with Mystery)

                          Instead of answers, more questions to be answered...
                          My maternal grandparents were married 61 years. My grandmother would have been 51 at the time, and I was with her often as I child. I thought my grandfather had a vasectomy, but that doesn’t prove anything.

                          Most importantly, when looking at shared relatives on ancestry, I see mystery man and I have shared relatives from both of my grandparents’ sides of the family which would negate the half-uncle possibility.

                          Comment


                          • #14
                            Originally posted by Emona View Post
                            Please be careful with X:

                            Someone wrote: "If you two are half siblings by the same mother, you would have a pretty sizable X-DNA match."

                            Not necessarily. You could share nothing in a rare but possible case: each one inheriting a different X. Mother has two X chromosomes.
                            I'll take an exception to the idea that two people with the same mother could have completely different X-chromosomes. That is a fallacy which has developed in genetic genealogy. It comes from setting the matching parameters too high. If you get no match, but you look at the chromosome browser and see lots of patches of green that make up about half of the X-chromosome, just lower the parameters.

                            Jack

                            Comment


                            • #15
                              Originally posted by georgian1950 View Post
                              I'll take an exception to the idea that two people with the same mother could have completely different X-chromosomes. That is a fallacy which has developed in genetic genealogy. It comes from setting the matching parameters too high. If you get no match, but you look at the chromosome browser and see lots of patches of green that make up about half of the X-chromosome, just lower the parameters.

                              Jack
                              In cca 98%, you are right. Most siblings do share some X-chromosome from their mother.

                              I have mentioned the remaining 2% of cases.

                              Mathematics:
                              In cca 1/5 cases, there is no recombination on X chromosome, in the process of making an egg in the human female.
                              (Got this number somewhere, can't find the source now. Please forgive me. Correct me and link to the source if you find different information.)

                              Take two children of the same mother: 1/5 times 1/5 = 1/25
                              It means cca 4% possibility of no recombination in both cases)

                              Then we have equally probable options:
                              1) child 1 has X-chromosome A, while child 2 has X-chromosome B from mother
                              2) both children have the same X-chromosome, whole length.

                              Result: Statistically cca 2% of pairs of siblings (or half-siblings with the same mother) will share no X chromosome from their mother.

                              Comment

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