A handful of families settled the western part of the county where I grew up. When I was a kid we'd have some fairly large family reunions on a Sunday afternoon every year. I'm at least distantly related to many family names there. It's entirely possible that people in a setting like that would pair up with a distant relative without even realizing it unless you went back 5 generations to check. I'd say that situation exists in many places. Maybe not so much today,..because people are much more mobile than they used to be.
Everybody has 64 great-great-great-great grandparents,...and the number of descendants that 64 people create gets very large. Anyone who is a member of a family that's lived in the same area for several generations will be blood relatives of a *bunch* of people in that area,..even some that they won't know.
