Cousin-screwing. It is not totally safe. It raises the risk of birth defects slightly. But I was reading in a book for history that there's, like, a 99.9999 percent chance that at least one of your great-great-great-grandparents married first cousin.
About This Quote
About John Green
John Green was a contemporary American author and youtuber. John Michael Green is an American author and YouTuber. His books have more than 50 million copies in print worldwide, including The Fault in Our Stars (2012), which is one of the best-selling books of all time. Read more on Wikipedia →