Yes, but I think that's the point. You *do* have a match through a third person. We now have four descendants of Isaac tested. Three match each other at the predicted 2nd-4th cousin level, but the fourth doesn't match *any* of the other three. It seems to me the probability that he is related is dropping... But I will give the other matching methods a try, to see if there's a match at a lower level. Diana > From: Marleen Van Horne > Sent: Saturday, February 11, 2012 1:03 AM > > Diana, > > I have a known cousin, her ggg-grandmother and my ggg-grandfather > are > brother and sister. She and I do not have an atDNA match, BUT we > both > have a match to a man who is a descendant, we think, of the brother > of > our gggg-grandfather. Go figure. > > Either situation is possible with your non-match. > > Marleen Van Horne