Genesis 35:22

35:22 While Israel was living in that land, Reuben had sexual relations with Bilhah, his father’s concubine, and Israel heard about it.

Jacob had twelve sons:

Genesis 36:12

36:12 Timna, a concubine of Esau’s son Eliphaz, bore Amalek to Eliphaz. These were the sons of Esau’s wife Adah.