If Adam and Eve were the only two human beings created by God, and then they had children, who did Cain and Seth marry? Or did God create other humans after Adam and Eve? Genesis 4.16.
I know this sounds like a silly question, but I have always wondered who their wives could be.
We have to remember that we have very little to go on to help us understand the passage of time in the early chapters of Genesis.
For example, we don’t know how much time transpired between Adam’s creation and the fall, or between then and the births of Cain and Abel. When Abel was killed both were adults, accountable to God and supporting themselves with their work.
According to Genesis 5:3 Adam was 130 years old when Seth was born, and he and Eve had other sons and daughters during the following 800 years. But since Genesis 5 opens a new segment in the Book of Genesis, we don’t know to what extent it overlaps chapter 4.
All that said, a literal reading of Genesis leads us to the conclusion that everyone on Earth at the time was a descendant of Adam and Eve. After Adam and Eve, God didn’t create any other humans.
Therefore, the most likely conclusion is that Cain and Seth each married one of their sisters.