Judaism considers the Jewish people to have 4 foremothers: Sarah, Rebecca, Rachel, Leah. I think it is time to go with 6. Bilhah and Zilpah should be added. They gave birth to 4 of Jacob's sons, so we contain their genetic material. They raised their sons and probably helped with Leah's and Rachel's. The fact that Jacob either didn't love them or loved them less should not be relevant. Neither should the fact that they were slaves, if they were.