Cain and Abel

Now Adam knew Eve his wife, and she conceived and bore Cain, saying, “I have gotten a man with the help of the Lord.”

Cain knew his wife, and she conceived and bore Enoch. When he built a city, he called the name of the city after the name of his son, Enoch.

And Adam knew his wife again, and she bore a son and called his name Seth, for she said, “God has appointed for me another offspring instead of Abel, for Cain killed him.”

But Onan knew that the offspring would not be his. So whenever he went in to his brother's wife he would waste the semen on the ground, so as not to give offspring to his brother.