I just came across a theory that Kylo Ren and Rey could possibly be half-siblings and I actually slapped my forehead like the emote. C'mon, it is obvious that it's the same story repeating itself. Twins separated at birth because darkness was sensed in their destinies, and just like when the first set of movies came out we will find out that our protagonist and antagonist are once again related and that once again two very important characters are actually twins. It's a nod to both trilogies. If Rey turns out to be the spawn of Luke I would be very upset. Luke is supposed to be the epitome of a Jedi, he should be a stoic as Obi-Wan and as wise as Yoda. I highly doubt that such a Jedi would break one of the most important codes of the order. That's my thoughts on it, Kylo Ren and Rey are siblings. That's why Rey had the visions of the dead Jedi younglings, that is also why when that vision ended the glowing from the engine was red, like the first order or Kylo Ren's lightsaber. I think Kylo Ren put her on that planet, and that is why he reacted so strongly when there was word of a girl, because she was supposed to be out of harm's way. Kylo Ren is constantly fighting the internal struggle between light and dark, I think that this is one of those battles, maybe even the one he plays closest to the chest.