Rey is the granddaughter of Emperor Palpatine. She is not biologically related to Anakin Skywalker.
From Star Wars: The Force Awakens' opening day, fans had their theories, and Star Wars: The Last Jedi seemed to squash all of them only for Star Wars: The Rise of Skywalker to provide a surprising answer: Rey is Emperor Palpatine's granddaughter, and her father a genetic strandcast (not quite a clone) of the Sith lord.
While on the planet, when someone asked her who she was, Rey responded by saying that she was "Rey Skywalker." Although she wasn't related to them, both Luke and Leia had been mentors to Rey throughout the sequel trilogy.
Rey is Anakin's half sister, and Palpatines relations to Rey through the force. Rey is a genetic experiment/force experiment of immaculate conception orchestrated by palpatine. So Rey is Palpatines daughter or grand daughter, in a metaphorical sense. The same way Anakin is Palpatines son through the force.
Kylo Ren (Adam Driver) was introduced as a knock-off Darth Vader in Star Wars: The Force Awakens, with good reason—he's Anakin's grandson. Similar to his grandfather, Ben Solo was once seduced by the dark side and goes on to wreak havoc in the galaxy.
Anakin Solo is the youngest child born to Han Solo and Princess Leia, and the younger brother of Jacen and Jaina Solo.
Anakin was actually the result of immaculate conception, so he doesn't have a father. His mother, Shmi Skywalker, conceived her child without a male partner, and instead Anakin was created through the Force.
She does not have a baby bump, her hand never goes to her stomach to indicate she's carrying a child, and there wasn't exactly any time for her to have conceived a child with anyone in the course of the film, including Kylo Ren/Ben Solo.
And in The Rise of Skywalker we finally learn that Rey is actually the granddaughter of Palpatine. Her parents—one of which is the child of Palpatine—abandoned her on Jakku to keep her safe from her grandfather who was aware of her power.
Following Palpatine's final defeat and her own resurrection, Rey adopts the name Rey Skywalker to honor her mentors and their family legacy and renounce her lineage. As the last remaining Jedi, she makes it her mission to rebuild the Jedi Order.
In addition to rejecting Sidious, Dathan married a woman named Miramir, whom he fell in love with. Together, they conceived a child, their daughter Rey, who was born in 15 ABY. Although he renounced the Sith Eternal and his donor, the Palpatine bloodline would prosper through him, just as Sidious predicted.
Rey's father was the cloned son, artificial genetic strandcast, of the resurrected Darth Sidious, making her the granddaughter of the fallen Galactic Emperor and Dark Lord of the Sith.
A crystal embodies the Jedi as the heart of the lightsaber, and pure kyber has no color until it's bonded to the Force user. This process likely resulted in Rey Skywalker's lightsaber being yellow.
What is the connection between Kylo Ren and Rey? As Kylo Ren himself says in The Rise of Skywalker, he and Rey are bonded not just by their familial legacies (Ren as the grandson of Darth Vader and Rey as the granddaughter of Emperor Palpatine) but by their unique connection in the Force.
The Last Jedi took the stance that Rey's parents were nobody, and while this may have been true from a certain point of view, The Rise of Skywalker gave us the true answer to Rey's parentage. In the film, we learned that Rey was a Palpatine, and her father was a clone of the infamous Sith Lord.
And because of this, Padme was reborn as Rey, ironically as the daughter of one of his clones, because Karma always comes back at you.
In the original Star Wars: Episode VI – Return of the Jedi screenplay, Obi-Wan did have a brother, and it was none other than Owen Lars (Joel Edgerton)—Luke Skywalker's step-uncle and Anakin's step-brother.
To Snoke, Rey was just a powerful Jedi to eliminate (more on this below). It wasn't until after the events of The Last Jedi that Palpatine recognized that Rey was his lost grandchild that he needed, and leveraged Kylo's inability to kill her by telling him to do just that - “Kill the girl”.
By the end of The Rise of Skywalker, Rey had become the last known Jedi of the Skywalker Saga. With all that being said, Rey was not left as the last remaining Force-sensitive character.
Ben grabs fertility beads off of her neck through their bond. When Ben brings her back to life he places his hand over her womb.
In a new excerpt, it's revealed that the names of Rey's parents are Dathan and Miramir. Dathan is the dad and Miramir the mother, if you were wondering; it's not always clear with these names from a long time ago in a galaxy far, far away.
A kiss of gratitude, acknowledgement of their connection, celebration that they'd found each other at last.
#1 – Yoda. Yoda is widely considered to be the greatest Jedi of all time, and with good reason. He is a master of the Force, a skilled warrior, and has an unmatched wisdom that comes from centuries of experience. He is the embodiment of what it means to be a Jedi, and his legacy lives on long after his death.
Anakin saw his mother again in a Force vision around 21 BBY on Mortis. The vision was induced by the Son, one of the powerful Force-wielders controlling the planet, through which the current of the Force flowed.
Darth Vader never knew he had twins until that final battle on the second Death Star. The force ghost of Obi Wan had warned Luke to bury his understanding of Leia deep or Vader would be able to sense his feelings.