Here's something interesting I came across while poking across the internet. Kylo going off the rails and murdering luke's students is a lot more recent than many of us have assumed.
Pablo Hidalgo is creative executive at Lucasfilm.
the incident "wasn't that long ago" and is "more recent" than 15 years ago. If we're generous and assume that " more recent" means 7 years ago and not like 3-5 years (which is what I'd go with), Then Rey (who is 19) would be at LEAST 12 when that attack happened.
She had already been on Jakku for years at that point. It's literally impossible for her to be Luke's child if that's the case, or for Kylo to have had anything to do with her placement there. She was there as a toddler (3, 4, something like that). The incident wouldn't have happened for a decade later.
She's not Luke's, and Kylo doesn't know her.