So I was wondering if its possible in any way to get a hint if someone showing as a 4th cousin match could be a 3rd cousin? From my understanding you can't, but I want to ask if anyone has done this or seen any clues in their matches. Since the daughter in laws matches are Japanese its very hard for several reason to work out how they are related on paper. She has one match thats 33cM over 4 segments plus a small X segment. My guess is maybe 3c1r. Other 4th cousin have one large segment 24cM another 22cM. I also see some matches having a huge amount of very small segments 4 to 5 cM and other matches a few or none. My thought is a closer match would have more small pieces simply because they are closer. I am just trying to make the best of a bunch of 4th cousins. Or maybe its more like banging my head against the wall.

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    I don't have a full answer for you, but be aware that there are arguments that matches are 4 to 5 cM aren't worth looking at because so many of them are false positives. Many tools have a default of at least 7 cM and some have a default of 10 cM. See Blaine Bettinger's blog: thegeneticgenealogist.com/2017/09/03/…
    – Jan Murphy
    Oct 8, 2017 at 8:57
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    Totally agree with @Jan Murphy. Unfortunately, matches below 20cM are not well suited for breaking walls in genealogy. But though they well work in terms of confirming paper genealogy. I.e. you know that somebody is your 4th cousin and you have match with this person, so it means that it is your 4th cousin :-) Also I want to emphasize that usually X match means nothing. It needs a lot of another data and specific processing to get additional clues Oct 8, 2017 at 13:10
  • Thanks for the replies. I did like the link to the small segments. I try to avoid them, however noticed a mother / daughter match had a very large amount of small segments. I wasn't sure if that might have meant something on its own. But I guess not. When you have one 3rd cousin match and a lot of 20cM and below matches there is not much to work with. I have found all the top matches above 18cM are all from the daughter in laws home town, except one and his father was adopted. We think he might be related to the 3rd cousin, same family name. Thanks again Alan
    – Alan
    Oct 9, 2017 at 11:15
  • As others have said, there's no real way of doing this because the range of cM one can share with a 3rd cousin starts at zero! I'd recommend doing some chromosome mapping so that you can see if these matches overlap the matches you have with with any known relatives.
    – Jonny Perl
    Oct 12, 2017 at 15:52


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