Introduction
Bilhah is a servant given to Rachel by her father Laban at her marriage to Jacob, later given by Rachel to Jacob as a surrogate wife to bear children in her name, becoming the mother of Dan and Naphtali, two of the twelve tribal ancestors.
Family
Surrogate motherhood
When Rachel, distressed by her own infertility, said to Jacob, "Here is my maid Bilhah; go in to her, that she may bear upon my knees and that I too may have children through her", following the ancient custom also seen earlier with Sarah and Hagar, Bilhah bore Jacob two sons, Dan and Naphtali, whom Rachel named and treated as her own.
Later episode
Genesis 35:22 briefly records, without extensive detail, that Jacob's eldest son Reuben "lay with" Bilhah, an act that Jacob is said to have heard of, and which later, in Jacob's final blessing in Genesis 49, is cited as the reason Reuben, despite being the firstborn, would "no longer excel" among his brothers.