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Benchmarking Known/Confirmed 3rd Cousins

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  • Benchmarking Known/Confirmed 3rd Cousins

    I have several 3rd cousins in 23andme and FTDNA and I would like to hear from forum members who have confirmed/known 3rd cousins they have tested regarding:

    1) Total amount of centimorgans (blocks/segements above 5 cM only please)
    2) Total number of segments above 5 cM
    3) Length of each segment above 5 cM

    Thanks!

  • #2
    Originally posted by nwgen View Post
    1) Total amount of centimorgans (blocks/segements above 5 cM only please)
    2) Total number of segments above 5 cM
    3) Length of each segment above 5 cM
    For two full siblings (i.e. the brother/sister values are not uncorrelated):

    3rd cousin via siblings mother:
    bro: 37.2 + 14.4 + 20.9 = 72.5
    sis: 7.8 + 7.8 + 15.0 + 20.9 = 51.5

    3rd cousin via siblings father:
    bro: 54.8 + 5.4 + 12.5 + 5.4 + 9.6 = 87.7
    sis: 56.4 + 53.8 + 5.4 + 5.4 + 19.5 = 140.6

    The 3rd cousins were found via traditional genealogy, they subsequently agreed to test.

    Raw FTDNA data compared by gedmatch.com using the 5cM threshold.
    Last edited by Lklundin; 3 September 2012, 03:54 PM.

    Comment


    • #3
      I am managing 2 siblings kits and have only confirmed two 3rd cousin 1x, each on seperate branches of paternal line. They only match on one sibling (gedmatch matches them to both)

      1) 3rd Cousin 1x

      Chromosome 2
      Start/End location: 23019126 to 31194150
      cM: 8.88
      Matching SNPs: 2100

      Chromosome 7
      Start/End location: 21764587 to 30177747
      cM:12.4
      Matching SNPs: 2784

      Total shared cM 21.28 >5cM

      plus an extra 13 locations smaller then 5cM

      2) 3rd Cousin 1x

      Chromosome 2
      Start/End location: 233444593 to 235338278
      cM:4.92 (included due to almost 5 and proximity of next segment)
      Matching SNPs: 886

      Start/End location: 235630142 to 239297057
      cM:7.09
      Matching SNPs: 985

      Chromosome 7
      Start/End location:17778322 to 29363846
      cM: 16.78
      Matching SNPs: 3884

      Total shared cM 28.79 >5cM

      plus an extra 13 locations smaller then 5cm

      Comment


      • #4
        I have several. I will post back as I get a chance.
        3rd Cousin 1R
        Shared cM 85.69 Longest Block 23.84
        6 blocks over 5 cM
        23.84, 16.05, 9.45, 6.52, 5.86, 5.13

        Comment


        • #5
          2nd once removed
          total cM above 5 cm : 66.19 cM (block 1, chr 1, 32.27 cM, middle of short arm; block 2, chr 2, 7.0 cM, near telomere; block 3, chr 9, 14.6 cM, near middle of short arm; block 4, chr 13, 12.32 cM, middle of long arm)

          2nd twice removed A
          total cM above 5 cm : 109.59 cM (block 1, chr 3, 6.04 cM, near telomere of short arm; block 2, chr 4, 5.57 cM, near telomere; block 3, chr 5, 13.62 cM, near middle of long arm; block 4, chr 9, 5.0 cM, near telomere of of long arm; block 5, chr 12, 50.86 cM, long arm; block 6, chr 16, 28.5 cM, near end of long arm)

          2nd twice removed B
          total cM above 5 cm : 85.60 cM (block 1, chr 5, 24.71 cM, near telomere of long arm; blocks 2-4, chr 6, around centromere, 3 blocks of 13.1 cM, 12.66 cM, and 29.87 cM; block 5, chr 7, 5.26 cM, near middle of long arm)

          2nd twice removed C
          total cM above 5 cm : 43.85 cM (one block, chr 6, 11700 SNPs, much of long arm)

          3rd once removed A (compared to sibling 1)
          total cM above 5 cm : 11.6 cM (one block, chr 4, 973 SNPs, near telomere)

          3rd once removed A (compared to sibling 2)
          total cM above 5 cM : 25.7 cM (block 1, chr 4, 11.6 cM, 973 SNPs, near telomere; block 2, chr 18, 14.1 cM, 2887 SNPs, near centromere)

          3rd once removed B
          total cM above 5 cm : 12.37 cM (one block, chr 14, 1777 SNPs, near telomere)

          Comment


          • #6
            This is very helpful. I'd love to hear from others. I have an unknown/unconfirmed suggested FTDNA "3rd cousin" with the following cM and segments:

            67.93 total cM in segments over 5 cM.
            4 segments of the following lengths: 19.04 cM, 17.84 cM, 15.28 cM and 15.77cM.

            Comment


            • #7
              Originally posted by nwgen View Post
              This is very helpful. I'd love to hear from others. I have an unknown/unconfirmed suggested FTDNA "3rd cousin" with the following cM and segments:

              67.93 total cM in segments over 5 cM.
              4 segments of the following lengths: 19.04 cM, 17.84 cM, 15.28 cM and 15.77cM.
              User John S Walden has created a plot that I find very useful for showing how likely a given match is to correspond to for example a 3rd cousin:

              http://forums.familytreedna.com/show...59&postcount=7

              According to that plot a value of 68cM is well within the range for a 3rd cousin. The value is however also consistent with relations from a 2nd cousin 1R out to a 4th cousin.

              PS. It would be interesting if more values could be collected for an update of this plot.

              Comment


              • #8
                Originally posted by Lklundin View Post
                User John S Walden has created a plot that I find very useful for showing how likely a given match is to correspond to for example a 3rd cousin:

                http://forums.familytreedna.com/show...59&postcount=7

                According to that plot a value of 68cM is well within the range for a 3rd cousin. The value is however also consistent with relations from a 2nd cousin 1R out to a 4th cousin.

                PS. It would be interesting if more values could be collected for an update of this plot.
                Thank you.

                Comment


                • #9
                  3rd cousin match (and same cousin as 3rd cousin 2r for myself)

                  3rd Cousin (Grandmother's kit and her 3rd cousin). This cousin is her strongest match (aside from myself) and was confirmed with a good paper trail.

                  1. 34.95cm (total cm inc. segments less than 5cm is 58.06)
                  2. only 2 segments above 5cm (13 total segments inc. all cm lengths)
                  3. chr 16 (6.63 cm) and chr 4 (28.32 cm)

                  This same cousin of my grandmothers (my 3rd cousin 2R) has the following segments between myself and her:

                  1. 27.79cm (total cm inc. segments less than 5cm is 51.98)
                  2. only 1 segment above 5cm (12 total segments inc. all cm lengths)
                  3. Chr 4 (27.79) (grandmother did not pass down the chr16 segment to me/got lost/too small in recombination)

                  * I also have 4 minor segments (between 1.45 - 2.91cm) that match the cousin and myself, and these 4 segments my grandmother does NOT match with her/doesn't have matching segments with her on those chromosomes at all. Guessing IBS rather than IBD, or possible shared ancestry from another grandparent (and likely not either of my grandfathers, but a very small chance of other grandmother).

                  Comment


                  • #10
                    Known/Confirmed 2nd through 5th cousins in FF

                    2nd – 13 seg 179.37 – 30.09, 24.28, 23.52, 18.74, 16.61, 16.39, 9.33, 8.3, 7.2, 6.56, 6.38, 6.12, 5.85

                    2nd – 12 seg 164.74 – 25.92, 25.88, 18.32, 12.98, 11.74, 11.55, 11.51, 11.15, 10.98, 10.1, 7.87, 6.74

                    2nd – 10 seg 138.37 – 32.9, 23.3, 17.06, 12.77, 12.03, 11.87, 8.9, 6.8, 6.43, 6.31

                    2nd – 7 seg 90.74 – 24.42, 21.73,11.22, 11.03, 8.77, 6.83, 6.74

                    2nd – 9 seg, 83.04 – 14.22, 11.62, 11.59, 11.27, 8.13, 7.82, 7.18, 6.17, 5.04




                    2nd 1x removed - 8 seg 137.29 – 31.94, 28.8, 26.9, 16.02, 15.34, 7.36, 5.66, 5.27

                    2nd 1x removed - 6 seg 125.83 – 38.97, 28.77, 20.31, 16.81, 15.65, 5.32

                    2nd 1x removed – 8 seg, 123.13 – 31.88, 24.14, 21.7, 19.26, 7.41, 6.93, 6.38, 5.43

                    2nd 1x removed – 5 seg 101.56 – 34.15, 23.6, 15.83, 14.74, 13.24

                    2nd 1x removed – 7 seg 80.4 – 20.36, 11.04, 10.63, 10.41, 9.89, 9.73, 8.34


                    3rd – 4 seg 84.06 – 29.23, 28.12, 14.74, 11.97

                    3rd – 2 seg 41.30 – 24.49, 16.81

                    3rd 1x removed – 1 seg 28.88

                    Half 3rd 1x removed (equivalent of 4th) – 1 seg 19.79

                    4th – 2 seg 44.07 – 29.22, 14.85

                    3rd 3x (equivalent of 4th 1x) – 2 seg 52.07 – 38.22, 13.85

                    3rd 3x (equivalent of 4th 1x) – 1 seg 14.57

                    4th 1x - 1 seg 24.92


                    4th 2x (equivalent of 5th) – 1 seg 26.61

                    4th 2x (equivalent of 5th) – 1 seg 24.32

                    4th 2x (equivalent of 5th) – 1 seg 12.56

                    4th 2x (equivalent of 5th) – 1 seg 8.51


                    Should note that for several of these, especially the closer ones, there were also segments in the 3-4.9 cM range not included here that are relevant, especially some located short distances from other segments on same chromosome or in same location as longer segment shares shown for closer relatives sharing with same cousin in question.

                    Comment


                    • #11
                      3rd cousin 1xR

                      Found via traditional genealogy. FF test cunfirmed relationship.
                      Shared cM : 31.50
                      Longest block : 16.75 chr 19
                      Total shared segments : 8 ( one 3+ chr 9; six 1+: chr #2,6,7 and two 1+ segments on chr 1

                      Comment

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