I had to take a little bit of time to ponder this new info. I'd been planning a different post on the movie (the DVD release has me excited to start talking about it again), but we'll just let that wait for some other time. For now let me get some thoughts out (probably nothing that hasn't already been said elsewhere, just my way of putting together what I think sounds most plausible). I also just want to record at what point I thought what--that way I can look back at this years from now and see how right or wrong I was.
When I first saw Episode VII, I was convinced Rey was Luke's daughter. Absolutely convinced. But the more I thought about it, the more boring that seemed. And then as time went on, my interest started to transfer from Rey to Kylo Ren. I went into it all loving Rey's character and walked out thinking only about Kylo Ren.
So by the time J.J. Abrams made his little declaration (which had better be true and not just a lie to throw us off the track), I was already feeling like Rey wasn't Luke's daughter after all. It's almost a relief now to think that she isn't and to feel like I don't have to keep wondering if that's true. Yes, the movie is constantly pairing her, visually, with Luke (her outfit looks like his Episode IV getup and her new outfit at the end of the movie closely resembles his Episode V look), but that can be because of theme instead of because they're related: her character can be playing the same role in this trilogy that Luke played in the OT. Like how BB-8 resembles R2 in some ways because he plays a similar role in the story as R2 did--not because he's a droid descendent of R2.
And now on to Reylo. I have confirmation (in this post) that I was considering the idea of Reylo at least by the second time I watched the movie. I figured that if the characters weren't related, then this was a way that they could be connected, with Rey possibly helping bring Ren back to the light side. And I thought it also made sense with the dual look the two characters have: one light and one dark, both paired together and reflected back on each other.
I thought about that. But I also apparently mostly dismissed the idea at the time (I still thought they were probably cousins). And now, well, I'm just like everyone else: I can't stop thinking about the idea of Reylo (I kind of like saying that name, too: it's funny).
It makes sense. I just rewatched the movie with this theory in mind. And if fits very well in his side: the complication's move on her side. Here is how I can picture it.
I tend to be interested in the theories that Ren is not all bad. We know that he was born with equal capacity for the light and dark sides because that's been stated (Even though that seems weird because how is that different from someone's free will to choose light or dark? Or does Star Wars believe in fate over free will now? Did it always?). The question is how much he wants to follow the light or dark side: everything he says and much of what he does is ambiguous. Is he ultimately trying to defeat Snoke by getting in close to his enemy? Is he trying to channel both the light and dark sides simultaneously to achieve the greatest power? Or is he just stumbling after mistakes he made because of his bad family life? We don't know anything for sure, but there is enough material like this that he isn't just a blank, evil character and therefore we can imagine how some type of relationship with Rey might develop.
Then watch the movie, watch his scenes with Rey, watch how he looks at her and what he says to her. He either knows something about her (her identity, her past, or the meaning of her strength with the Force) or he loves her (either romantically of platonically). He does look her up and down when he first meets her--in a completely ambiguous way (Adam Driver certainly knows his acting); he might be kind of checking her out or simply sizing up his enemy. He obviously grows fascinated by her, which could be because he likes her or simply because of her power (or, of course, both). When he takes off his mask in the interrogation scene, it's as if he wants her to see his face. Because it'll make his task easier? I don't see how. So it can only be because he wants her to see him as human and not the "creature in a mask." Either because some part of him wants her to like his face or because he is hoping to get her to join him on the dark side and showing his humanity seems like a good way to do this. (Or he might remove his mask to see if she recognizes him from the past, to test and see if she is who he thinks she might be. But I'm not sure about that one: it seems possible that they might have known each other in the past, but that would need a lot of explaining.)
Then there's this. Both novelizations (adult and junior editions) have Ren telling Rey that he's going to take the map from her mind and to not be afraid. But the movie's line is a little different. There's a gap after he talks about taking the map and then he says, "Don't be afraid. I feel it, too." Feel what? The presence of the map? No. Her fear? That seems more likely (though this would more be him thinking he feels her fear but actually he's the one who's afraid). Someone said it's the connection between them. Maybe.
In both novelizations is also the line from Snoke: "You feel compassion for her?" Ren denies this but the fact that Snoke says it must mean there's some truth to it. The question is whether he means compassion as in sympathy or as in Anakin's definition that he gave to Padme in Episode II (basically, love).
If Ren's attracted to Rey, then that would easily give a reason for him not wanting to kill her in the final lightsaber battle (I can't quite bring myself to believe that he was really trying to defeat her, for whatever reason). After all, in the beginning he just throw her at a tree and fights Finn instead--then she has to peskily start a fight with him. He offers to teach her. How's that for a pick up line: "I can show you the ways of the Force." Could be because he wants her to stay with him or just because he knows she's strong and wants her on his side.
What makes me pause so much is his expression after she beats him. There he is on the ground, all wounded and cut up and defeated--and he looks maybe like he's having an out of body experience, maybe he's a little shocked but mostly he just looks still. Kylo Ren, still. Usually when things don't go his way or he gets shocked he reacts by getting angry and throwing a tantrum and slashing things with his lightsaber. Obviously he's very injured here so that affects how he can react, but he doesn't even look angry. Whatever it is, there has to be a reason why he isn't angry at Rey: if it had been anyone else defeating him he would have been angry. But because it's her he isn't.
So in the future I think there will be even more scenes between these two characters. Possibly they may shift light/dark roles (Rey has to get tempted by the dark side at some point, just as Luke was. Maybe Kylo Ren himself will be her temptation.). Possibly a love story will develop (Ren has to either come back to the light side or be revealed to be secretly working for the good all along for this to happen: no one's advocating a creepy attacker/victim relationship here. Even if Rey joins him on the dark side, I still don't think that would make up for how he treated her.). But they are for sure connected in some way, even if it is just thematically.