Overview
Milcah ( Mīlkā, related to the Hebrew word for "queen") was the
daughter of Haran and the wife of Nahor, according to the genealogies of Genesis. She is identified as the grandmother of Rebecca in biblical tradition, and some texts of the Midrash have identified her as Sarahs sister.
Sister of Sarah
One of the Yahwist passages from Genesis identifies Haran as the father of Iscah and Milcah. Some rabbinic texts within the Midrashic tradition have identified the aforementioned Iscah as Sarah. According to the Babylonian Talmud, Rabbi Isaac Nappaha, who was one of the Palestinian rabbis, said that Iscah and Sarah were the same person: "And why was she called Iscah? Because she saw through the Holy Spirit".
Ancestor of Rebecca
She is identified as the grandmother of Rebecca in the Book of Genesis, but some scholars believe that Milcah may have originally been Rebeccas mother. They have argued that Bethuel, who is identified as Rebecca's father by the priestly source, was a later addition to the text, and that Rebecca was the daughter of Milcah and Nahor.
According to Bible in the book of Genesis 24:15, Milcah is the Grandmother of Rebecca and her father is Bethuel.
From Wikipedia (CC BY-SA 4.0).