Genesis 25 says these twin sons of Rebekah even struggled against each other in their mother's womb
Genesis 25:19  36 (Isaac, Jacob, Esau) | Bible.org [PAR] Jan 3, 2013 ... 25:22 But the children struggled inside her, and she said, If it is going ... 25:24 
When the time came for Rebekah to give birth, there were twins in her womb.