In The Rise of Skywalker, Rey learns that She is, in fact, the granddaughter of the big baddie of the nine Star Wars films, Emperor Palpatine.
In The Last Jedi, Rey learns that her parents were nobody special. It added something special to the legacy of Star Wars: that an individual’s lineage didn’t define their connection to the Force.
In Star Wars Episode III: Revenge of the Sith, Anakin Skywalker raids the Jedi Temple, and eventually finds a room full of children. Anakin pulls out his lightsaber and murder of children is totally the most unforgivable act and probably the moment when there’s no turning back from his Darth Vader destiny.
Ray's actual origin should have been that she belonged to that group of Jedi Order's small training children. She was then the youngest, hid and survived. She may even have been on arriving stage, and the massacre took place before she joined the group. In a miraculous way, she was transffered to another planet. She grew up there and learned few practices of the Force. She stayed young thanks to anti-aging treatments.
This narrative could explain everything about Rey, and add many new dimensions to her charater, without a need for a Dark Force's legacy.
The toddler years are a time of great cognitive, emotional and social development.
