Genesis 29:30-31

29:30 Jacob had marital relations with Rachel as well. He loved Rachel more than Leah, so he worked for Laban for seven more years.

The Family of Jacob

29:31 When the Lord saw that Leah was unloved, he enabled her to become pregnant while Rachel remained childless.

Deuteronomy 21:15

Laws Concerning Children

21:15 Suppose a man has two wives, one whom he loves more than the other, and they both bear him sons, with the firstborn being the child of the less loved wife.