Do the probabilities at Family Tree DNA for TMRCA between two men based on STR markers also hold true even if the two men do not share the same surname? When describing what matching at the 67 marker level means, Family Tree DNA prefaces their statement by saying, "A XX/67 match between two men who share a common surname (or variant) means...". So I'm not sure how accurate STR matching probabilities are for two men with different surnames but who share the same Haplogroup, i.e. I-P109. Does the fact that we don't share a common surname change the probabilities for TMRCA in any way based on STR matching? At the 67 marker level, I only have matching with two men who do not share my surname. My surname is Simonds, and based on 67 markers, Family Tree DNA says that I have a 98.7% probability of sharing a common ancestor with someone named Lambert within the last 24 generations which I would calculate at about 720 years or 30 years per generation. It says that I have a 99.72% probability of sharing a common ancestor with someone with the surname Diver within the last 24 generations. It's interesting to me that these two families, the Diver and the Lambert families, lived within less than 10 miles of each other in the early 17th century. The ancestor of Diver (kit # 42300) was baptized at Isleham, Cambridgeshire in 1618 while the ancestor of Lambert (kit 206903) was supposedly married at Cavenham, Suffolk in 1624. Isleham, Cambridgeshire and Cavenham, Suffolk are (according to Google Maps only about 9.9 miles from each other. My own ancestor William Simonds was born in England in 1611, although I don't know for sure where in England he came from. But I had already thought even before I did any DNA testing that he might have come from Suffolk since there are many Simonds/Symonds families who were living there since at least the beginning of the 15th century. Can I assume based on my STR matching with the Diver and Lambert families that my own Simonds family did indeed come from this same area of East Anglia and that the Diver, Lambert and Simonds families had a common paternal ancestor there within at least the last 720 years or sometime in the 1200s? Matthew Simonds P.S. For purposes of comparison with someone from my own surname, I have a match with someone that I know to be my 9th cousin with ten generation separating us. Family Tree DNA says that we have an 88.29% probability of sharing a common ancestor within the last 12 generations.