Genesis 24:59-60

"And they sent away Rebekah their sister, and her nurse, and Abraham's servant, and his men. And they blessed Rebekah, and said unto her, Our sister, be thou the mother of thousands of ten thousands, and let thy seed possess the gate of those that hate them."

"And her nurse ..." This person was named Deborah (Genesis 35:8). "Possess the gate of ... etc." These words were spoken by God himself to Abraham upon the occasion of the sacrifice of Isaac in Genesis 22, and their use here by Laban and his brother would indicate that some contact between the two families had been resumed after Abraham learned about them (Genesis 22:20ff).

"Their sister ..." The only other person in view, besides Laban, in this chapter who could also have been Rebekah's brother was Bethuel, giving inferential support to our understanding Bethuel to have been not her father, who was dead, but another brother. "Their sister" is not appropriate as a reference to a relationship between Rebekah, and Laban and Rebekah's mother.