I've thought personally that the scene is tragic to see, after earning Rey's love, he dies for her. Why couldn't they have been together and have a "happily ever after"?
I've personally thought they'd make a nice couple and ship them a lot together. Ben giving up his life for her has been tragic and terribly sad in my eyes at least anyways.
Before she's known that she's his sister, she has been having feelings for him. I don't think it could be called incest because she hasn't known about it personally.