I have a fourth cousin, let's say Dorothy, who doesn't match me or my 4 siblings and first cousin. I don't know how likely this is but I think it could happen. I've looked for gedmatch segments down to 3CM with no matches. Then I tested a second cousin of Dorothy's, Bart, who matched Dorothy appropriately. All eight of us are on Gedmatch. The Dorothy group of two doesn't match any of the 6 in my group. Bummer. However, Bart is a 7 CM match on chromosome 12 with a sister and me on 23andme. 13 CM is the average amount that 4th cousins would share and the range is from zero to quite a bit. I'm not overly surprised that a small match on 23andme disappears when transferred to gedmatch but it complicates my testing. So, how likely is it that the two groups are related or not related? I'm sure the answer is to find more cousins to test. I have no 2nd cousins on this line. I talked to a 3rd cousin on this line that wouldn't take a DNA test:( Any thoughts and recommendations appreciated before I break the news to Bart & Dorothy. Cheers, Jim