Airs Sunday, May 24th at 10/9c. Part of BBC America Reveals.

Most societies consider incest to be the ultimate taboo. Yet, a strange phenomenon called ‘Genetic Sexual Attraction’ has been known to affect adults who meet long-lost blood relatives for the first time.

This program features several brother/sister couples who’ve developed sexual relationships and insist on maintaining them in spite of pressure from society and, sometimes, criminal prosecution.