I've suspected Rey to be a Skywalker for some time now, although probably from Leia and Han. It's possible she's Luke's kid. I've suspected her to be a Jedi since I saw the movie poster, with the staff paralleling Ren's lightsaber being symbolic. Twins would make that parallel even more significant.

The trailer for all the Star Wars have been amazing. Watching the ep. 1-3 trailer now and saying it looks bad doesn't do it any justice, you have to consider it within the culture of the time they came out. Back then they were amazing. It's just as true with the trailer's for ep. 4-6. If you watch them today they're all awful, but I'm sure they were awesome at the time they were actually on tv.