One of the Yahwist (contested) passages from Genesis identifies Haran as the father of Iscah and Milcah.
According to Genesis Chapter 22, Milcah and Nahor have eight children: Uz, Buz, Kemuel, Chesed, Hazo, Pildash, Jidlaph, and Bethuel.
[7] Targum Jonathan says that Providence granted Milcah conception in the merit of her sister Sarah.
[8] Milcah's son Bethuel moves to Padan-aram (also called Aram-Naharaim) and fathers Rebekah.
And in the Talmud, Rabbi Isaac equates Milcah's sister Iscah with Sarah (then Sarai), in which case Abraham would have married his brother Haran's daughter.