Isaac had two sons, Esau and Jacob.

In complete opposition to the customs of that time, God chose Jacob, the younger son to be heir to His promises.

In fact, before these twins were born, God had revealed to their mother Rebecca, the future of her two sons. "Two nations are in your womb. Two peoples separated from your body; One people shall be stronger than the other, and the older shall serve the younger." Genesis 25:23