[See Jacob's Family Tree]
She was one of Jacob's wives. Originally Laban's maidservant, Laban gave her to Leah as a maidservant when Leah and Jacob married.
After Leah bore four sons, she gave Zilpah to Jacob as a concubine, and Gad and Asher were born from Jacob and Zilpah.
Gen 30:9When Leah saw that she had stopped bearing children, she took her servant Zilpah and gave her to Jacob as a wife.Gen 30:10And Leah's servant Zilpah bore Jacob a son.Gen 30:11Then Leah said, "Good fortune!" and she named him Gad.Gen 30:12Leah's servant Zilpah bore Jacob a second son.Gen 30:13Then Leah said, "Happy am I! For the women will call me happy." And she named him Asher.