(Only a minor spoiler here. Reading this won't ruin the movie for you, but you will have a greater understanding when the part comes in the movie that is about to be discussed.)
There's a scene in "The Last Jedi" where Rey thinks she's about to find out her parents' identities. We see two silhouettes in front of her before they're reduced to one and Rey is staring back at herself. This is very common in children raised in a closed adoption. Staring at the mirror and wondering if you are an alien hybrid or related to someone famous. Any person who is adopted can relate if they can remember a time when they didn't know any biological relatives. The lack of mirroring is detrimental to the identity of the adopted person.
Many theories have come up on who Rey could be. She's a Kenobi. She's a Skywalker. Maybe the studio truly wanted to catch fans off guard by sending a message that anyone can be born Force sensitive. This would explain all of the young lings at the temple and the little boy you see sweeping out the stables on Canto Prime.
One of the biggest questions fans had at the end of "Star Wars: The Force Awakens" was the identity of Rey.
Viewers finally received some sort of answer in "The Last Jedi," but it wasn't really satisfying. And like many adopted people when told who their parents were, hard to accept without proof.
(This is your last chance to head back before spoilers.)
Near the end of the film, Kylo Ren and Rey are speaking. Rey is consumed with learning the identity of her parents. Ben tells Rey that she knows the truth about her parents. She has known it all along. The problem? She doesn't want to accept the truth. Ben can see what she will not. Ben tells her that she's nobody. She came from nothing. Rey had filthy, poor parents on Jakku who sold her for drinking money. That's it. That's the big twist.
"They were filthy junk traders," Solo tells her. "You have no place in this story. You're nobody. He also says they're buried in pauper's graves. There is no more finding out. No more answers to her questions. Just nothing, pain and death. This happens a lot to adopted people who wait too long to search or are unable to because of current laws. A headstone, more questions and regret.