One of our readers, Elizabet, made this suggestion of 7 in the Bible,

How about the 7 explicitly named ancestresses of Israel? There’s Sarah, Milcah (grandmother of Rebekah), Rebekah, Leah, Rachel, Bilhah, & Zilpah. Though Milcah was not wed to any of the 3 patriarchs (Abraham, Isaac, & Jacob) she was a biological ancestor of Rebekah, who was a mother of Israel herself. 

Thank you, Elizabet, for your keen observation!