Zilpah

Zilpah was the maidservant given by Laban to his daughter Leah as a wedding gift, and she later became a concubine of Jacob (Genesis 29:24; 30:9–13). When Leah stopped bearing children for a time, she gave Zilpah to Jacob, and Zilpah bore him two sons: Gad and Asher. These two sons became heads of two of the twelve tribes of Israel, making Zilpah's biological contribution to the nation foundational despite her status as a concubine rather than a primary wife.