I sort of have an ongoing debate with a co-worker regarding the wives of Seth and Cain (Adam and Eve’s sons). My co-worker asked me where did they come from as there is no clear explanation in Genesis and they just sort of appear. I say that they have to be descendants of Adam and Eve who are the mother and father of mankind. My co-worker feels that this would be incest and can’t be. Can you clarify this for us?
Adam and Eve were the first humans and Cain was their first son, so he had to have married either a sister, a cousin, or a niece. Genesis 5:4 tells us that after Seth was born, Adam and Eve had other sons and daughters.
Since Cain was worried about being killed, some of Adam and Eve’s other offspring were obviously of an age to avenge their brother Abel’s death so there could easily have been a female suitable in age to be Cain’s wife.
The notion of incest was unknown in those days. For instance, Abraham married his half sister Sarah (Genesis 20:12), Rebekah was Isaac’s niece (Genesis 22:20-23), and two of Jacob’s 4 wives were his cousins as well as being each others’ sisters (Genesis 29:10,16).