Deuteronomy 21:15
If a man have two wives and loves one more than the other. The first son of either wife is the man's first-born son, even if the boy's mother is the wife he does not love. A man near death and dividing up his property must give a double share to his first-born son. This is because he was the first to be born.
Genesis 29:33
She became pregnant again and gave birth to another son. She said: Certainly, Jehovah has heard that I am unloved. He has also given me this son. She named him Simeon.
1 Samuel 1:4-5
The day came for Elkanah to make his offering. So he gave a part of the feast to Peninnah his wife, and to all her sons and daughters.
Genesis 29:18
Jacob was in love with Rachel, so he said: I will work seven years for you, if you will let me marry Rachel.
Genesis 29:20
Jacob worked seven years for Laban. The time seemed like only a few days, because he loved Rachel so much.
Genesis 29:30-31
Jacob slept with Rachel too. He loved Rachel more than Leah. So he worked for Laban another seven years.