I left the theater after my first (and even second) viewing entirely convinced that Rey is Luke Skywalker’s daughter. Duh. All signs point to this (the inheritance of the lightsaber, Maz Kanata’s cryptic insights, the final scene with Luke, etc). After all, the whole story is about the sins and redemptions of the Skywalker family, right?
While Ben’s theory is plausible, I don’t believe the writers were clever enough to come up with it. Oh, it’s full of spoilers, so don’t bother reading it until you’ve seen ‘The Force Awakens’.