From The Urantia Book:

(76:2.9) And so Cain departed for the land of Nod, east of the second Eden. He became a great leader among one group of his father’s people and did, to a certain degree, fulfill the predictions of Serapatatia, for he did promote peace between this division of the Nodites and the Adamites throughout his lifetime. Cain married Remona, his distant cousin, and their first son, Enoch, became the head of the Elamite Nodites. And for hundreds of years the Elamites and the Adamites continued to be at peace.

Jesus himself commented on this occurance, and linked it to the idea of “original sin” as a result of the default of Adam and Eve:

(148:4.7) “You are confused, Thomas, by the doctrines of the Greeks and the errors of the Persians. You do not understand the relationships of evil and sin because you view mankind as beginning on earth with a perfect Adam and rapidly degenerating, through sin, to man’s present deplorable estate. But why do you refuse to comprehend the meaning of the record which discloses how Cain, the son of Adam, went over into the land of Nod and there got himself a wife? And why do you refuse to interpret the meaning of the record which portrays the sons of God finding wives for themselves among the daughters of men?”

Thank you for your question. The Urantia Book is a treasure trove of information regarding the Garden of Eden, the default of Adam and Eve, the second garden, where Cain was married, and the destiny of all of these important figures in our distant history. Please go here to read the complete story of Adam and Eve, and you can gain new insight into the meanings of it even in our present day.