I know that much. Rey is probably Luke's daughter with some contvient wiped or repressed memories so she is powerful and has latent trauning. Just taking it in the movie on its own it comes off a bit odd. My guess is that Kylo Ren and Rey are uber powerful Skywalker while Finn can use the force but has the whole Vegeta has to train and work for it arc.
If you want to get rid of choosen ones in teh Star Wars universe, nuke desert planets from orbit.