Who was Cain's wife? Where did she come from?
His sister or a close relative. Adam and Eve "begat sons and daughters" (Gen 5:4), and in the first generations siblings married of necessity, no genetic danger yet and no law against it until Moses.
What the text states
Adam had "sons and daughters" (Gen 5:4) beyond the named ones and lived 930 years, so there were many children. Cain's wife was a sister or niece. Close marriage was not sin then, the command came at Sinai (Lev 18), and the genetic problems arise only after generations of accumulated mutation. On the young-earth view, with all humanity from one couple, close marriage in the first generations is exactly what the Bible requires.
Skeptics use Cain's wife to argue Genesis is incoherent, assuming unrelated people. We hold the text's own answer: Adam's many other children, and no barrier before Sinai.
Go deeper
Checked 2026-09-29 by Darren. 50 Scripture citations verified against the KJV rows. Wave 4. 50 quoted fragments table-passed against the verses table, splitting every quotation at its ellipsis. 49 pass. ONE CORRECTION: the file quoted "Dead in sins" (Eph 2:1); the KJV reads "dead in trespasses and sins", and the quotation was corrected to the table. One exhibit does not resolve and ships omitted rather than guessed: what-does-dead-in-sin-mean listed 'is-faith-a-work', which is not a slug on this site (the nearest is is-believing-a-work); flagged for Darren.