I predicted this. The context, though, was conservative clergy and other privileged men secretly fathering large number of children in small towns or long-lived church groups, then having those children marry each without realizing the relationship. The small town where a third of a generation resembles a popular local preacher is a standing joke in Texas.
DNA TESTS ARE UNCOVERING THE TRUE PREVALENCE OF INCEST

People are discovering the truth about their biological parents with DNA—and learning that incest is far more common than many think.

It’s so common because people are not aware they’re doing it.