I'm trying to determine how 2 men and my brother have the same terminal haplogroup. Which surname, if it can be determined, he belongs to. We have an NPE in this line as it is and this makes it harder to figure. At this point, can you even determine who did what, when to know? Where do you even start?

FTDNA has the 'mean' about 1500CE. That is so far back, clear back to when the ancestors lived in England and would be our 10Grandparents at min. There is a 4th that matches but he hasn't done Y-700 and is cousin to the other two men. Those 3 men share a surname. Does this mean it is so far back that in general it doesn't matter what the surname is/should be? Records really don't exist for back then and there is no way to use autosomal DNA beyond 5th Grandparents.

Our bio dad is deceased and our half brother doesn't care to test. Thanks