In Joseph and the Technicolor Dreamcoat, a reoccurring theme is Jacob’s twelve sons. What isn’t apparent from Dreamcoat is many of the sons were half brothers; Jacob was indeed the father of all, but there were four different moms.
Here is how this convoluted family tree happened:
Jacob fell in love with Rachel (his uncle’s daughter, that is, his first cousin). Since he had no dowry, he agreed to work for his uncle seven years for her hand in marriage. The morning after the wedding, he discovered that his veiled bride was actually Leah, Rachel’s older sister. He had been duped by his Uncle Laban. After protesting, Laban also gives Jacob Rachel’s hand in exchange for another seven years of labor.
Leah begins having children (six sons in all), but Rachel is childless — so she has her husband sleep with their maid, Bilhah, to produce children in her stead; Bilhah has two sons. In an escalating competition, Leah follows suit, giving her maid, Zilpah, to sleep with Jacob; Zilpah also has two sons.
Finally, Rachel gets pregnant and has Joseph. As the first-born of Jacob’s favorite wife, Joseph is doted upon by his father; hence he is given the infamous coat of many colors, thereby earning the wrath of his brothers. Later, Rachel also gives birth to Benjamin, the youngest of the twelve; sadly Rachel dies in childbirth.
Although the nation of Israel is launched through these twelve sons, Jacob’s family life is a lesson of everything not to do.
[Genesis, chapters 27 through 29]