Thank you for the question, “Why did Jacob have children with the servants of his wives?”
Here are some thoughts on why Jacob was intimate with the maids of his Rachel and Leah:
A. Jacob was faithful to Rachel and Leah in his marriage to them.
B. Rachel was unable to conceive a child from Jacob.
Genesis 30 says this: “When Rachel saw that she was not bearing Jacob any children, she became jealous of her sister. So she said to Jacob, “Give me children, or I’ll die!” 2 Jacob became angry with her and said, “Am I in the place of God, who has kept you from having children?”
C. Rachel gave her maid, Bilhah to be his wife so that Rachel can have a child through her.
Genesis 30 says this: “3 Then she said, “Here is Bilhah, my servant. Sleep with her so that she can bear children for me and I too can build a family through her. 4 So she gave him her servant Bilhah as a wife.”
It was the custom of that period that if a wife was unable to conceive that she can have another woman bear a child for her. In order for the child to have status in the community, he had to marry her otherwise that child would be consider illegitimate.
It is also important to note that Jacob didn’t rape Bilhah. Rachel insisted that Jacob marry Bilhah which he did and then he slept with her. Bilhah’s status in Jacob’s household was his third wife.
D. Leah was also jealous of Rachel decided to do the same thing with her maid when she was no longer able to conceive a child. She gave Zilpah to Jacob as his wife as well. Zilpah’s status in Jacob’s household was his fourth wife.
Genesis 30 says this: “When Leah saw that she had stopped having children, she took her servant Zilpah and gave her to Jacob as a wife. 10 Leah’s servant Zilpah bore Jacob a son” (NIV).
I feel sorry for Jacob with his two wives battling each other for his affection. They involved their maids who became Jacob’s third and fourth wife.
SUMMARY: Jacob married Bilhah and Zilpah at the insistence of Rachel and Leah to give more children. It was a battle of who would have more children through Jacob. Each of them wanted the undivided love of Jacob.