While Israel lived in that land, Reuben went and lay with Bilhah his father's concubine. And Israel heard of it. Now the sons of Jacob were twelve.
Genesis 35:22
It was common practice in the ancient world for a usurper to take the deposed ruler's wives in a show of dominance. Reuben sleeping with Jacob's concubine, Bilhah, was a failed coup attempt. By taking one of his father's wives, he was making a claim to his father's place in the household. He's fortunate that he only lost his place as firstborn and not his life.
"Anyone with whom you find your gods shall not live. In the presence of our kinsmen point out what I have that is yours, and take it." Now Jacob did not know that Rachel had stolen them.
Genesis 31:32
So Rachel died, and she was buried on the way to Ephrath (that is, Bethlehem)...
Genesis 35:19
Was Rachel's untimely death in Genesis 35:19 a direct result of the rash curse that Jacob pronounced on the idol thief in Genesis 31:32? I suspect so. The words of a father and husband have real power in his family. Be careful what you say.
And God said to him, "I am God Almighty: be fruitful and multiply. A nation and a company of nations shall come from you, and kings shall come from your own body."
Genesis 35:11
In this verse, God repeated to Jacob the command to be fruitful and multiply. The command applies to all mankind, but it is doubly important for God's faithful remnant to be fruitful, both naturally and spiritually. The world needs good people. We can create them by saving the lost or by making babies. Best to do both!