So here are my thoughts on Rey's parentage.
Rey is Luke Skywalkers daughter AND Kylo Ren's brother. Boom!
Kylo Ren is actually Ben Solo. But why would Han and Leia name their child after Ben Kenobi? Leia never actually met him, only heard about him in passing from her dad and knew his name as Obi-Wan not Ben. Han Solo met him as Ben, and his entire interaction with him was to call him a hokey old space wizard and insult his religion. They had no business naming their son Ben. Luke on the other hand loved Obi-Wan like a father figure. So my theory is Luke had twins, Rey and Ben. For plot reasons he had to give them up, and Han and Leia adopted Ben. When they discovered he was force sensitive (probally by force choking puppies) they sent him back to Luke to be trained and he went to the dark side.
This would bring back the Jaina/Jacen twins plot line from legends which it seems like it was already going to with Rey and Kylo.