Since the news broke that Emperor Palpatine is actually a clone, fans have been clamoring for more information about what The Rise of Skywalker novelization will reveal about the film. Rae Carson's book was available for purchase weeks ahead of its official release at the recent C2E2 convention in Chicago. One fan who managed to get hold of an early copy described a massive reveal that complicates everything we thought we knew about Rey's lineage.
Michelle of the Unknown Regions podcast devoted a two-hour episode (later posted on Reddit by user Alcida-Auka) to breaking down all the details from the Rise of Skywalker novelization. At around the 22-minute mark, she explains how Sheev Palpatine "yeeted his soul" from his falling body into a clone before he hit the ground.
Lots of fans had suspected as much, even if this was poorly explained in the movie. The next reveal was totally unexpected, though. Turns out, Palpatine's cloning method was imperfect. The first, failed clone had "perfect body," but Palpatine was "unable to occupy it" and the clone had no Force sensitivity. (So where did Rey inherit that Force lightning from? Does it skip a generation, like hair loss?)
That clone was Rey's father. Presumably, at some point Palpatine let this perfect-bodied clone loose to procreate with an unknown woman and create Rey. This makes the young Jedi's relation to him a bit... murkier. Cloning, from a scientific perspective, is the replication of someone's DNA. Biologically, Rey has half of Palpatine's traits, making her his daughter.
Aside from the sketchy family tree, why would Palpatine release a clone? The podcaster says Palpatine wanted Rey because she was "naturally conceived." So the release of the clone ensured an organic birth of someone with half Palpatine's DNA. While we still may not know her parents' actual names, this clue means Rey's connection to the Sith Lord is even closer than we already knew thought.
This may all have been in the first draft of The Rise of Skywalker: there were rumors that Doctor Who alum Matt Smith would appear, but he was never cast or his cut from the film. A vocal segment of fans became convinced Smith would play a young Palpatine or Rey's dad. While that, for one reason or another, never made it to the silver screen, fans can read all about it in the upcoming novel.
The Rise of Skywalker: Expanded Edition debuts March 17, 2020.