People often ask the question, “Who is Cain’s wife?” A proper response to this question is to ask in return, “Who was Seth’s wife?” The answer to both questions is the same: they married their sisters. People often ask this question because they don’t know what the Bible says about incest. The modern-day definition of incest is based on ideas about breeding offspring from genetically close parents, but in the ancient world, siblings, half-siblings, and cousins married all the time. How else would there be “royal bloodlines” in various cultures?