Who did Cain marry?
The question is based on the information that Adam and Eve, the first human pair, had two sons, Cain and Abel. The Bible records how Cain killed Abel. That gives rise to the question, how then was Cain able to find a wife and carry on the race?
The answer is that Adam and Eve had additional children besides Cain and Abel. There was a third son named Seth, born after Abel’s murder, and additional children followed who are not named:
​
“This is the book of the generations of Adam. When God created man, he made him in the likeness of God. Male and female he created them, and he blessed them and named them Man when they were created. When Adam had lived 130 years, he fathered a son in his own likeness, after his image, and named him Seth. The days of Adam after he fathered Seth were 800 years; and he had other sons and daughters” (Genesis 5:1-4).
Cain and Seth married their sisters and had children by them. As Cain appears to have been born in the first year after Adam’s fall, Seth was 130 years younger than Cain, and Seth’s sisters could well have been younger still. It is thus very likely that there was a major difference in age between Cain and the sister whom he married and therefore they did not grow up as siblings together in the same household.