WARNING: The following article contains spoilers for Star Wars: The Rise of Skywalker, in theaters now.
J.J. Abrams first introduced the mystery of Rey's parents in The Force Awakens. Rian Johnson then attempted to offer fans a challenging answer to the mystery in The Last Jedi -- that her parents were no one of importance. The Rise of Skywalker then confirmed that her parents were, ultimately, unimportant to the narrative. But, the film also revealed that Rey's grandfather happens to be very important: Sheev Palpatine, making the Emperor the central antagonist of the entire Skywalker Saga.
The knowledge that Rey's father was, in fact, the child of the galaxy's most diabolical antagonist is shocking enough. However, it also opens up a whole barrage of unfortunate implications. One is that every one of her mentor figures apparently knew her to be Palpatine's child this whole time but didn't tell her. But there's another wrinkle created toward the end of the film, and it's to do with the fact that being a progenitor of Palpatine means she may have a second cousin: Ben Solo.
THE SKYWALKER/PALPATINE FAMILY TREE
A young Anakin Skywalker was introduced in The Phantom Menace, where we learn from his mother that he had no father. Instead, he was born from the Force itself; an immaculate conception, in other words. There are two ways we could interpret this: one is that the Force produced a child with a woman (fulfilling the "Chosen One" prophecy, as Qui-Gon argues), and the other is that someone used the Force to create a child.
The latter theory is given more credence when we reach Revenge of the Sith. In that film, we see Anakin fear for Padme's life. He has visions of Padme dying in childbirth, which leaves him vulnerable to Palpatine's manipulation. It's at Anakin's lowest point that he meets Palpatine in a theater, where he tells the young man the story of Darth Plagueis the Wise.
Darth Plagueis figured out a way to use the Force to create life. That he learned how to keep those he loved from dying is a secondary effect of his discovery. However, Palpatine assures Anakin that not only could Plagueis create life, but he also taught his pupil everything he knew -- before said pupil killed him in his sleep.
We know Palpatine was Darth Plagueis' pupil, which means he had the ability to create life himself. Some fans believe Palpatine used that ability to create Anakin Skywalker, which explains why Anakin was so strong in the Force. The theory is heavily implied in 2018 to be canonical by way of Marvel's Star Wars comics.
KISSING COUSINS
It might be a stretch to call Anakin Palpatine's actual son, considering Palpatine's non-consensual impregnation of Shmi Skywalker required no exchange of genetic material. However, he was still "created" by Palpatine's machinations, if the comics are anything to go by. That means Luke and Leia would be Palpatine's grandchildren, of a sort, and that Ben Solo would be Palpatine's great-grandson.
Rey is more directly related to Palpatine, as she is his genetic granddaughter, which makes her Ben Solo's second cousin. Neither her nor Ben would share any genetic material, but they come from the same source. That might explain their intense connection to one another: They are related.
This finally brings us to that moment at the end of The Rise of Skywalker, where Ben shares one kiss with Rey before passing on, having used his life force to revive hers. If they are indeed second cousins, this would make their shared kiss yet another incestuous one, echoing the one Luke and Leia shared during The Empire Strikes Back, which itself was made ickier by the 1978 novel Splinter of the Mind's Eye (a sequel to Star Wars), which depicted Luke lusting over his sister.
OTHER UNFORTUNATE IMPLICATIONS
In case you needed more reasons to feel uncomfortable, there is more reason to believe that Rey and Ben Solo's relationship is a little more familial than it is romantic -- despite their passionate kiss. It's obvious that Rey Palpatine and Ben Solo are inspired by Han and Leia's children, Jaina and Jacen Solo, from Legends lore, as their paths through the films follow very similar trajectories.
However, beyond that, comments made by J.J. Abrams on the subject indicate Rey and Ben were actually written as siblings -- or, at least, with the intention of appearing like siblings.
"There's as much of a brother and sister thing with Rey and Kylo Ren as there is romantic," the filmmaker said. "So it's not literally a sexually/romantic kind of thing. It's more like they're just bound together in this crazy, spiritual way. Again, felt romantic to me."
So, is it a familial relationship or is it a romantic one? If we look at it through the lens of Rey and Ben Solo being part of the same family, then that kiss is even more confusing. Abrams also compares the kiss to the kiss shared between Luke and Leia -- neither of whom really knew they were siblings beyond Leia's confused, "I always knew" admission in Return of the Jedi. All it really confirms is that there's hardly a single romance in Star Wars that is straightforward. And we know, after all, the Dark Side is a pathway to things some would consider to be "unnatural."
Directed and co-written by J.J. Abrams, Star Wars: The Rise of Skywalker stars Daisy Ridley, Adam Driver, John Boyega, Oscar Isaac, Lupita Nyong’o, Domhnall Gleeson, Kelly Marie Tran, Joonas Suotamo, Billie Lourd, Keri Russell, Anthony Daniels, Mark Hamill, Billy Dee Williams, and Carrie Fisher, with Naomi Ackie and Richard E. Grant.