Rebekah's father was named Bethuel, but is possible that Rebekah also had a brother by that name as well. Due to the way the story is worded in Genesis 24, has led some commentators to believe that Rebekah’s father was dead and that the Bethuel mentioned in the story was in fact her older brother by the same name. Three reasons they give for this are: 1. Laban's name is mentioned before Bethuel's. If Bethuel was the father, he should have been first, with Laban secondary. 2. Laban and Rebekah's mother speak up on her behalf at her betrothal. No mention of her father. 3. The only mention of Bethuel is when both Laban (Laban is first) and Bethuel tell Eliezer that this marriage arrangement is from the Lord.

One other reason to consider is that when Rebekah does leave with Eliezer to travel to meet Isaac, her family blesses her. When they do so, they call her "Our sister". Not "our daughter".

Not factual proof, but reason enough to allow for the possibility, yes?