church of Christ
      Who did Cain take as a wife?
                
TA Baisden

If you notice in the bible God gives the genealogy or family line of the male so as to be able to follow that's male's seed through out the written word, whether they were godly or sinful men their seeds was still noticed. Most of this was done of course to show the earthly side of Jesus or his fleshly ties to human beings through David and his seeds Mary and Joesph who was Jesus adopted father,
(this link will tell you more about this) who God gave the care of his son while he live on earth as a child. The bible speaks very little on the line of any female seed but does at time speaks of them having daughters. Just as they speak the given names of Jesus earthy brothers in Mark 6:3 but only that he had sisters no given name was listed for them. Well this is basicly the same rule even as far back as Adam, does this mean there were not female born to these males. No, of cousre not they just were not mentioned by name usually. You noticed that Adam and Eve had daughters but they were never mention by name or birth. I at time wonder if Cain and Able were not twins for in Gensis 4:1-2 doesn't speak of Eve conceiving again it just said she bore Able, but of course for certain I do not know this to be the case. Would there have been other children born to Adam and Eve by the time Cain was old enough to kill Able. God told them to be fruitful so my answer would be, Yes. So who did Cain take for a wife, it would have had to have been one of his sister.