The Family of Cain
Then Cain went out from the presence of the LORD and dwelt in the land of Nod on the east of Eden. And Cain knew his wife, and she conceived and bore Enoch. And he built a city, and called the name of the city after the name of his son--Enoch. (Genisis 4:16 & 17) (NKJV)
In that scripture, it doesn't say that Cain met his wife in the land of Nod. It says "Cain knew his wife". In this scripture "knew" means that Cain had sexual relations with his wife, "knew" is used in a few other scriptures to mean, sexual relations. Also in other translations, say for example NIV it says "Cain lay with his wife, and she became pregnant and gave birth to Enoch" (pretty self explanatory)
Also, I gather that, as right after it says Cain knew his wife, it states that his wife bore their son, Enoch. Usually before you have a child, you have sex.
So, why would we believe that he met or married his wife in the Land of Nod? He may have married her and taken her with him to the land of Nod.
So, it leads one to believe that perhaps Cain married one of his "sisters".
Remember in those days the people lived directly under God's Law! People also had no choice but to marry their "brother" or "sister". If you look at the bible in context we are all desendants of Adam and Eve and that would make us all brothers and sisters??
Also, if we go back and read Genesis, people at that time (such as Adam) had a VERY long life span. Remember, after Seth was born the bible states that Adam lived another 800 years, altogether Adam lived for 930 years. The bible also states in the same scripture that Adam went on to have other children. If the human life span was around 900 years or so, could you imagine how long the childbearing years would have been for a woman? Imagine how many children Adam could have fathered...there could have been a huge population boom....
Cain could have married anyone of the daughters that Adam fathered...
Love & Blessings!