How did the Alabama incest trope originate? Was there a widespread issue with siblings having children?

by tnick771
Broke22

More can always be said, but take a look at this excellent answer from /u/sunagainstgold

https://www.reddit.com/r/AskHistorians/comments/6itg5p/in_popular_culture_and_meme_posts_theres_a/