Warning, if you don't want to know major parts of the TFA story, don't read no further. My colleagues and I, all scientists with doctoral degrees in either astronomy or physics and working at a large research institution, had a meeting this Friday to discuss the upcoming events of the force. That's what we found out, and thus I write it in really tiny font:
The movie is a big family reunion. Rey is the daughter of Leia and Han, but grew up in the UK. She is fighting against Kylo. Maybe Kylo is female, as TheOrcKing logically suggested before, and I have the same observation in mind since the first trailer. It would make sense because it would fit the idea of two powerful but opposite women, Rey and Kylo. This will be revealed perhaps in episode 8 or 9. Kylo is Rey's cousin, because Kylo is the kid of Luke. Luke trained her/him as a Jedi. Luke and R2D2 live like hermits on the Dagobah swamp planet similar to Yoda before him; we saw them in trailer #2, just look at Luke's mechanical hand. Kylo's mother died early, perhaps during a brutal killing. So Kylo did experience a similar traumatic event like his grandfather, Anakin/Darth. As we know from the studies by Sigmund Freud et al., childhood traumas can have very damaging consequences. This is why Kylo--same as Anakin--could not resist the dark side, and no hope and no love can reach his/her mind and soul. Kylo constructed her/his self-made lightsaber and wants to finish what his/her grandfather started. Finn is a non-clone storm trooper, and he turns into a Jedi, with a regular blue (like Luke's) lightsaber. It could be that his father is Lando from Bespin, or maybe Finn is much closer related to Rey and Kylo.
That's it for now, please don't hesitate to post your comments and suggestions and we can discuss them at the next meeting:)