The thread is getting pretty long, and I'm not sure your question was answered. A 10 cM segment should be pretty robust, but it wouldn't hurt to verify that all of the pairwise comparisons hold up. IF it should happen to be a false positive, you and your half-brother would be saying the same thing twice, which doesn't make it any truer. Ann Turner On Sat, Jan 7, 2012 at 1:11 PM, Marleen Van Horne <[email protected]> wrote: > If any of the following represents a misunderstanding on my part, please > correct me, gently. > > I had my half-brother FF tested. We share the same father. Any matches > we have over 10 cM should be consider IBD. > > Of the 7500 total cM of atDNA, approximateley 3750 cM can come from one > parent. I realize this division can be flexible. Of that approximately > 3750 cM, my brother and I actually share 1607.60 cM of atDNA. The > largest segment is 196.19 cM, on chr 4. > > My half-brother has 83 FF matches without me. I made a list of all his > > 10 cM matches and compared the names to my list of matches. He has > 41 matches > 10 cM, of those sixteen names are on my list of matches. > > I then downloaded the list of matching locations for these 16 people for > both my half-brother and me to a Excel spreadsheet and sorted the > information by chromosome and starting location for the matching segments. > > Most of the > 10 cM matches are on chr 4. My expectation would be that > our matches on chr 4 should also match one another to some degree, as > many of their location overlap with one another. > > First, is the above correct? > > Second, what is the best way to proceed? >