In my experience a 102 cM match across 7 segments at Ancestry is
unlikely to be a false positive, but more likely a 3rd to 4th cousin
as Ancestry predicts.
Do you and your match really know all the descendants of all your
great-great-grandparents? I sure don't. Heck, I don't even know all my
If you don't know all your great-grandparents siblings and all their
descendants, then you are going to find names that you don't recognize
on your DNA matches >from when female descendants marry. You may want to
try working on the trees for both you and your match to find the most
likely sources of connection. If you have cousins that have tested, that
can really help narrow things down.
Sometimes the DNA test results can lead you directly to the paper trail
that shows you the breakthrough and the connection. Other times you do
the research as far as you can, but then have to wait until you
eventually find another clue that makes the connection. And sometimes
you run into an NPE which can be really difficult to untangle.
Ancestry is remarkably good at taking care of false positives for
Jewish DNA results, at least through the upper parts of the 3rd-4th
cousin matches. The area that I still wonder about though are matches
with 100 cM or less but many more segments, say 10 or 12. Those seem
to me more likely to be over-estimated at Ancestry.
Los Altos, California