I don't know whether it has happened to you before but some people seem to be just dating people from a particular tribe.I have a friend who was always dating Masai girls and it went on like this till eventually married a Masai. (Please note that i don't imply that Masai are bad).
I know most us do not ask tribe in the beginning of relationship, Is your dating pattern skewed to a particular tribe? What tribe have you dated most and why?