Kylo Ren was the main villain of the Star Wars sequel trilogy - and little by little, tie-ins are revealing his backstory. When Lucasfilm launched the sequel trilogy, they placed Kylo Ren at the center of their marketing. He was presented as a powerful Force-user who bore a not-coincidental similarity to Darth Vader, but his true identity was carefully concealed until Star Wars: The Force Awakens. There, viewers learned Kylo Ren was Ben Solo, the son of Han and Leia.
Star Wars is well known for its transmedia approach, with Disney frequently using tie-ins to explore backstories and add in crucial detail. This hasn't really worked well for the sequel trilogy, however, probably because they didn't really have things planned out in advance. Thus the story of the sequels consists of a vast number of course-corrections, with character arcs adjusted in response to an increasingly divided - and divisive - fanbase. That's had a particularly frustrating effect on Kylo Ren in particular, whose backstory was finally revealed in Star Wars: The Last Jedi but was subject to a number of retcons ahead of Star Wars: The Rise of Skywalker. Now, rather than the next Darth Vader, he is a very different character; where Darth Vader sought to conquer the dark side, Kylo Ren was effectively imprisoned by it. When he told Rey to "surrender" to the dark side, he was unwittingly hinting at his own relationship with it; he had never truly chosen the dark side, but rather had been overwhelmed by it.
All these retcons make it quite difficult to piece together Kylo Ren's history. In the Disney era, everything is supposed to be equally canon, including every tie-ins; but there are a number of contradictions in Kylo Ren's backstory, and it's interesting to try to explain them away. Meanwhile, there are still substantial gaps as well, and oddly enough those are particularly notable from the point he joined the First Order. Still, accepting those limitations, here is everything we know to date.
The Birth of Ben Solo
Leia Organa had always known her son was strong in the Force, able to sense his presence even while he was in her womb. She usually sensed him as a pillar of light, but occasionally became aware of a vein of darkness running through the child. Though Leia did not know it, this is actually quite unusual; children don't usually demonstrate any Force alignment at all, let alone fetuses. On one disturbing occasion, detailed in Chuck Wendig's Aftermath trilogy, Leia became aware of a mysterious dark presence watching over her son. This was presumably the resurrected Emperor Palpatine. Fixing his covetous eye on the grandson of the Chosen One as a potential host, the Emperor established a secret Force Bond with the infant, one he would use to corrupt him.
The son of Han Solo and Leia Organa, he was born on the same day the New Republic and the Empire signed the official Galactic Concordance, finally bringing an end to the Galactic Civil War. This was a heady moment in the galaxy's history, and the birth of a child seemed like a symbol of hope. Ben appears to have been something of a celebrity from the outset, carrying a heavy weight of expectation upon his shoulders because of his parents' identity.
The Childhood of Ben Solo Was A Troubled One
Ben was strong in the Force from an early age, but his childhood was a troubled one, likely exacerbated from Palpatine's influence. His parents seem to have been reluctant to encourage Ben in the ways of the Force, concerned he would fall to the dark side. It didn't help that their marriage was a troubled one, because neither Han nor Leia were willing to compromise their own lifestyle. Ben seems to have been something of a father's boy, and so as Han began to travel the galaxy more, Ben spent substantial time on the Millennium Falcon. This may well explain how Ben came into contact with Supreme Leader Snoke, a genetically engineered being created by Palpatine and introduced into galactic society.
Ben Solo Became Luke Skywalker's First Student
As revealed in the Star Wars: The Rise of Skywalker Visual Dictionary, Ben Solo's parents came to realize their son couldn't just have an ordinary childhood. Thus they asked Luke Skywalker to train Ben as his first Padawan, and Luke was more than happy to do so. Honoring Han and Leia's wishes, Luke too concealed the truth about Ben's grandfather from him, carefully avoiding telling him he was the grandson of Darth Vader. Luke remained blissfully unaware of Supreme Leader Snoke's influence on Ben; he had no idea the Emperor had created a Force Bond, and was using Snoke as his mouthpiece to manipulate the teenage Jedi Apprentice.
He may have officially been Luke's Padawan, but there's some evidence it was a strange, half-apprenticeship, with Ben spending a substantial amount of time with his dad on the Millennium Falcon as well. Charles Soule's The Rise of Kylo Ren includes a flashback to this period, with Ben accompanying Luke on a mission. "I'm glad you came along, Ben," Luke told his student, suggesting this wasn't the norm.
Ben Solo Encounters the Knights of Ren
This mission was to a Rim world called Elphrona, site of a Jedi Temple settled during the High Republic Era. Palpatine took this opportunity to bring Ben into contact with another of his pawns, Ren, and Ben was found himself strangely fascinated by the Knights of Ren. Although they could not defeat Luke Skywalker in battle - indeed, the Jedi Master easily bested them - Ren made an appeal to Ben. "You sure this is the life for you," Ren asked. "You do know there are other paths, right?" He had planted a seed, reminding Ben there were other paths than the ways of the Jedi.
Ben Solo Learns His Grandfather's True Identity
Ben Solo was 23 years old when he finally learned the truth about his heritage - and he did so in the worst way possible. Leia Organa was campaigning to become the next Chancellor of the New Republic, and in Claudia Gray's novel Bloodline her political rivals discovered a long-lost message from Bail Organa recounting her family history. The Senators feared history was repeating itself, that the daughter of Darth Vader was manipulating political events to her own end just as Palpatine had done all those years ago. They played the recording at the Senate, to Leia's horror. Her political career lay in ruins, the galaxy now knew who Leia and Luke really were - and Ben was finally forced to confront the truth. No doubt this shook Ben to the core, adding credence to the whispers of Palpatine, Snoke, and Ren, the voices who had told him he was of the darkness and not of the light.
Ben appears to have now headed to Luke Skywalker for further training, perhaps indicating a growing gulf between the young man and his parents. By now Luke had established his own Jedi Order, and the Master's attention was divided. He seems to have initially denied the truth he sensed, that the dark side was strong in Ben, perhaps unwilling to confront such a painful reality. Besides, Ben seemed to be doing so well, flourishing in the ways of the Force. Ben was a Skywalker, with all the natural power that comes with the Skywalker bloodline, and he took pride in his accomplishments in the Force.
A Fateful Confrontation Between Luke Skywalker and Ben Solo
As told in Star Wars: The Last Jedi, one fateful night Luke Skywalker entered his nephew's chamber and looked at him with the Force. It's unclear what exactly Luke saw; whether he saw Ben's own darkness, or whether - more likely - for an instant the Emperor revealed his presence. Whatever the truth may be, Luke reacted on pure instinct, and triggered his lightsaber. Ben awoke, and in his sleep-fogged state he engaged his uncle in a desperate duel. The full story of this battle is told in The Rise of Kylo Ren, which reveals Ben Solo was goaded on by Palpatine's voice, the Emperor cheering as uncle and nephew fought to the death. Ben triumphed, bringing down the building on Luke Skywalker; he probably won because his uncle's heart wasn't in it.
This was the moment the Emperor had been waiting for. With Luke Skywalker defeated, Palpatine summoned a Force Storm and unleashed it upon the Jedi Temple, killing all Luke's other students. Only three Jedi Padawans survived, having been offworld, and upon arriving they assumed Ben was the one responsible for the tragedy. Still reeling, Ben blamed himself, and fled to Snoke for guidance.
Ben Solo Becomes Kylo Ren
Snoke sent Ben Solo to the Knights of Ren, supposedly to train under them but in reality to push him to embrace the darkness. The Emperor orchestrated something similar to a Sith initiation ritual, in which Ben was supposed to choose to kill someone he cared about; but, while Ben did indeed kill his last friends among the Jedi, he fought against the darkness every step of the way. In the end, Ben's "good death" was actually Ren himself, and he claimed the position of Kylo Ren, leader of the Knights of Ren. This moment sent shockwaves through the Force, and - though Ben didn't know it - it seems to have triggered Ben's Force Dyad with Rey. Over on Jakku, a young girl suddenly felt cold even in the heat of the blazing desert sun.
Kylo Ren Was Integrated Into The First Order
The next few years are something of a mystery, little explored in the various Star Wars tie-ins, and the early relationship between Snoke and the First Order at this stage is unknown. It's unclear just how long Snoke had been Supreme Leader of the First Order; some comments in Delilah S. Dawson's Phasma suggest it was only after Kylo Ren sided with Snoke that he reached out to the former Imperials who were regrouping in the Unknown Regions. Whatever the case may be, Kylo Ren was inserted into the First Order's power structure.
At the same time, Kylo Ren became increasingly focused on his grandfather's legacy, believing Darth Vader's supposed "redemption" was a moment of weakness; in truth, he looks to have simply been attempting to justify his own inability to resist the dark side, to be master of his own circumstances. The First Order essentially erased all record of Ben Solo's existence, presenting Kylo Ren as though he had simply emerged from the shadows with no origin, and Kylo Ren seldom removed his mask unless he was alone or in the company of Supreme Leader Snoke. Some, such as Armitage Hux, sensed the falsehood - and resented Kylo Ren's position.
Snoke Continued Kylo Ren's Training
Supreme Leader Snoke continued Kylo Ren's training, and according to the Star Wars: The Rise of Skywalker Visual Dictionary he taught him secrets of the dark side such as the Mind Probe. As seen in the Age of Resistance: Snoke one-shot, the Supreme Leader privately looked upon Kylo Ren's attempt to reinvent himself in Vader's image with scorn. He attempted to manipulate Kylo Ren by pushing him, driving him to fear and anger. Finally, Snoke took Kylo Ren to the Dagobah System, where he told him to enter a cave steeped in the dark side - the same one Luke Skywalker walked into in The Empire Strikes Back. There, Kylo Ren was confronted first by an image of his uncle and then by his parents. His challenge was to kill them, and to Snoke's delight he passed. Snoke was less pleased when Kylo Ren lashed out and destroyed the cave in a telekinetic temper tantrum.
The Quest For Luke Skywalker
The First Order prepared to launch their attack on the New Republic, which would begin with the destruction of Hosnian Prime; that would be the beginning of a Blitzkrieg in which their forces swept across the galaxy, terrifying and intimidating everybody. But the First Order began to hear rumors of a map that would allow them to find Luke Skywalker, who had hidden himself away on the forgotten Jedi Temple world of Ahch-To. The First Order learned this was in the hands of Lor San Tekka, a member of the Church of the Force, who Kylo Ren had met when he had traveled the galaxy with Luke Skywalker many years ago. Kylo Ren took personal charge of the search for Lor San Tekka, as detailed in the Star Wars: Battlefront II story mode. This path led him to Jakku, and marks the beginning of the sequel trilogy, in the opening scenes of Star Wars: The Force Awakens.