To continue the rehash tradition and expand it on trilogy level? If EP8 reveals that Rey is related to someone we already know, this will be downright ridiculous.
So if she’s related to a pre-established character, that immediately makes it a total rehash?
whutI hate how there are lightsabers in TFA. Total rehash.
I think characters are part of a story that unfolds in a specific way.
Lightsabers are furniture of the Star Wars universe to be used by the characters as required by the story. Such as hyperspace, droids, the force etc.
TFA mercifully restricts their use to plot devices portraying them as quasi-mythical. Luke’s is kept hidden until discovered by Rey. Ren’s is custom made and a symbol of his character’s struggle to emulate his grandad.
If Rey is related to any previous character that really would be a major rehash, specific to the plot.
Better if she is random. She could be from a family that believed in and taught about the force. Such teaching may have become forbidden after Luke’s failure to train more Jedi without awakening the dark side in others. Snoke and Ren’s training would have the opposite effect in stirring the force to “awaken” in Rey - as well as guiding BB8 into her hands. Perhaps she can be the one that balances the light and the dark side within herself and so achieving what Luke couldn’t.
She definitely shows a few tinges of the dark side in the movie.