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.
Lot of areas like that including my home county. Don't think I have any recent common ancestors with myself, but my parents families both lived within about 5 miles from one another in a rural county for about 150 years, would be surprised if there wasn't some overlap with distant cousins somewhere down the line. A cousin did a family history book on one branch of the family a few years ago tracing them back to when they first came to America in the 1600s, seems the same 5-6 families all lived next to each other since the 1700s and several of them would all pick up and move a little further west with each other.
