My parents were cousins, so they'd known one another all their lives. (It was legal for them to marry at that time and in our home state.) They were happily married for 28 years, until my father's death. I was only three when that happened, but growing up, my mom would always tell me she'd never had a stranger in her bed. As a kid, I somehow found that comforting. As an adult, I realized it mostly just sounds creepy - LOL.