I have found half a dozen people who have almost exact matches of 19.85 cM (4,600 SNP's) on Chromosome 18 and few other matches above 5 or 6 cM elsewhere. I have looked at what I can find of the family trees of these people (the people I have contacted have been very helpful). The best I can do is to put the six or so into three quite different tribes. All are Ashkenazi but their known roots (locations) are far distant. Has anyone else found so many multiple matches on a single chromosome with far distant....too far to be really related....individuals? Statistically, I would think that a longest block of this size MUST indicate a common ancestry not that many generations back.
Can anyone help with this puzzzle?
(I am helping two adoptees to find their roots. Both are among the half dozen with this particular near-exact match. Their birth dates are over forty years apart!)