If you haven't yet seen Star Wars VII, turn away!
For the rest of us, YouTuber Mr Sunday Movies has an interesting idea about who Rey might really be. According to his theory, Rey is actually the granddaughter of Obi-Wan Kenobi, born of a child he fathered during the gap between III and IV. It's certainly a less obvious theory than the one that frames her as Luke's daughter, but it would make for a nice twist, and an opportunity for Star Wars to not treat its audience like a bunch of idiots who need to be hit over the head with symbolism.