I was taking a walk yesterday, this friendly woman said hello, I stopped to talk to her, about Christianity, she said the Bible is not accurate, I said why do you say so, she said that who did the children of Cain and Able marry? I said, in those days they lived for a thousand years during those days there must have been thousands of children born, she replied so they committable Incest? did they have a choice, they had to work with what they had. "Say Eve asked Adam, will you be faithful. That would have been a foolish question. Let's face it she was his "Rib to begin with" is that Incest? You can't get more into it than that?
any way this is what is said about the subject. Genesis 4:17 And Cain knew his wife,.... Who this woman was is not certain, nor whether it was his first wife or not; whether his sister, or one that descended from Adam by another of his sons, since this was about the one hundred and thirtieth year of the creation. At first indeed Cain could marry no other than his sister; but whether he married Abel's twin sister, or his own twin sister, is disputed; the Jews say (g), that Cain's twin sister was not a beautiful woman, and therefore he said, I will kill my brother and take his wife: on the other hand, the Arabic writers say (h), that Adam would have had Cain married Abel's twin sister, whom they call Awin; and Abel have married Cain's twin sister, whom they call Azron; but Cain would not, because his own sister was the handsomest; and this they take to be the occasion of the quarrel, which issued in the murder of Abel.
And she conceived and bare Enoch; which signifies "trained up", not in the true religion, and in the ways of God and godliness, as one of this name descending from Seth was, who is said to walk with God; but in the practices of his father Cain, and in a wicked course of life:
(For Cain to marry his sister or any other close relation was not harmful as it is today. There would be few if any genetic disorders at this time. However, as time past, the human race accumulated more and more genetic defects.
[So by the time of Moses, the laws against incest, as given in Lev_18:1, were necessary. These laws helped prevent deformed children. Ed.)]
I found the answer, its all in the Bible:
Lev 18:1 The LORD told Moses
Lev 18:2 to tell the people of Israel: I am the LORD your God!
Lev 18:3 So don't follow the customs of Egypt where you used to live or those of Canaan where I am bringing you.
Lev 18:4 I am the LORD your God, and you must obey my teachings.
Lev 18:5 Obey them and you will live. I am the LORD.
Lev 18:6 Don't have sex with any of your close relatives,
Lev 18:7 especially your own mother. This would disgrace your father.
Lev 18:8 And don't disgrace him by having sex with any of his other wives.
Lev 18:9 Don't have sex with your sister or stepsister, whether you grew up together or not.
Lev 18:10 Don't disgrace yourself by having sex with your granddaughter
Lev 18:11 or half sister
Lev 18:12 or a sister of your father or mother.
Lev 18:13 (SEE 18:12)
Lev 18:14 Don't disgrace your uncle by having sex with his wife.
Lev 18:15 Don't have sex with your daughter-in-law
Lev 18:16 or sister-in-law.
Lev 18:17 And don't have sex with the daughter or granddaughter of any woman that you have earlier had sex with. You may be having sex with a relative, and that would make you unclean.
Lev 18:18 As long as your wife is alive, don't cause trouble for her by taking one of her sisters as a second wife.
Lev 18:19 When a woman is having her monthly period, she is unclean, so don't have sex with her.
Lev 18:20 Don't have sex with another man's wife--that would make you unclean.