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  • Can anyone explain this?

    I am new to the forum and apologize if this is not the right place to ask.My 2nd cousin and I share the same gr.grm. and with Family finder are 143 cm shared and longest block is 39.I have recently had a test done with a lady who has the same birth name as our gr.grm. and is of the same ancestry.My cousin matches the lady at 84 cm and longest block is 15.However I am nowhere on the lady's list of cousins.Hope someone can offer insight to this problem.

  • #2
    It is possible -- and far from certain based on just this evidence! -- that the lady in question is a third cousin of you and your second cousin. There is a significant chance that actual third cousins will not show up as matches. This happens in about 10 percent of third cousins, and about 50 percent of fourth cousins. It is a matter of the luck of the draw, that you didn't happen to end up with a large enough matching segment to be detected as a match with her, but your second cousin did. Remember that it is also possible that your new match is related in some other way to your second cousin but not to you. You may be able to find additional shared matches that will give you stronger evidence. It could be helpful to make a careful inventory of the segments that you and your second cousin share, and to seek other matches that both you and your second cousin match on those same segments. If you are able to recruit additional known relatives, that will make it much easier to understand what the genetic data are trying to tell you. At least to start with, I would recommend ignoring segments less than 10 cM.

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    • #3
      Can you determine how this lady may be related to you and your second cousin, using paper genealogy? Could she be related more closely to your 2nd cousin than you? The 84 cM that your 2nd cousin shares with the woman gives a variety of possible relationships using the Shared cM Project Tool at the DNA Painter website. Most likely are half cousin relationships, or removed cousin relationships to various degrees, although 3rd cousin to your 2nd cousin is a possibility.

      The probability of sharing no DNA increases from 2.30% for a third cousin, then jumps to 12.10% for a 3rd cousin once removed, and 30.70% for a 4th cousin. And it gets higher from there. There are two blue charts showing the probabilities of shared DNA between levels of cousins or great-grandparents, from 1st cousin to 6th cousin once removed, and 1st to 14th g-grandparent, at the ISOGG Wiki's Cousin statistics page.

      Is it possible that your relationship to the woman with the same name and ancestry as your g-grandmother may be more distant than your 2nd cousin's relationship to her? You might ask your 2nd cousin to see if his shared matches with this woman include you, but it is most likely they do not. If you are above a third cousin to this woman, you can see from the chart that you may not share any DNA with her, simply due to how matching DNA to her was randomly not inherited by you, but was inherited by the 2nd cousin.

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      • #4
        Thank you for sharing your thoughts.I am leaning towards me not having enough of my gr.grm.'s dna to register.It all just seems odd to me.A bit of genealogy,Harvey's gr.father was my gr.father's 1/2 brother but both had the same mother,Eliza Sherwood.a daughter of Samuel Sherwood and Catherine Steep. Harvey is my second cousin.He is 89 and I am 73.Maria born Sherwood in Ireland is according to Ftdna is a 3rd to 5th cousin of Harvey.Living in a small rural place Steep's and Sherwood's intermarried.I don't know of your thoughts about Gedmatch but comparisons between Maria and me autosomally estimates 7.4 gen to mrca,Harvey and Maria 4.2 gen,Ken my 2nd cousin once removed(a Morley) and Maria 4.8 gen and Linda a Sherwood descended from a brother of my gr.grm. 4.6 gen to mrca. Strange,eh.
        Last edited by George Morley; 19 July 2020, 09:44 AM. Reason: Corrected an error in lineage

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