A visitor writes,
"Where did Cain and Abel (before he was slain) get their wives. The Bible only record more children of Adam and Eve after the birth of Seth"
Eve is the mother of all living.
Genesis 3:20 And Adam called his wife’s name Eve, because she was the mother of all living.
So notwithstanding that the Bible does not record it, Cain must have married one of his sisters.
I hope you find this helpful,
God bless,
Glenn