Ben Solo, the son of Han Solo and Leia Organa, was born roughly a year after the Battle of Endor. At some point in his youth, Ben trained as a Jedi apprentice under his uncle, Luke Skywalker. However, he was drawn to the dark side of the Force by Supreme Leader Snoke of the First Order. Ben adopted the name "Kylo Ren" and joined a group of dark side users called the Knights of Ren, who killed all of Luke's other apprentices.
The Force Awakens
Luke Skywalker disappeared since the destruction of his new Jedi Order, and Kylo Ren, who became a commander in the First Order, began searching for him. His quest brought him to the planet Jakku, where the last piece of a map leading to Luke's suspected location was held. On Jakku, he crossed paths with Poe Dameron, who had been sent by General Leia Organa of the Resistance, and captured him. Ren failed to retrieve the piece of the map, which Dameron stored in his astromech droid, BB-8.
In the chase for BB-8, Ren was brought to the planet Takodana, where he encountered Rey, a scavenger from Jakku. Ren managed to capture Rey with little difficulty.
Some time later, the Resistance launched an attack on Starkiller Base, the planet-sized superweapon of the First Order. A group consisting of Han Solo, Chewbacca, and Finn infiltrated Starkiller Base to rescue Rey and to assist the Resistance's X-Wing fighters in destroying the weapon. Although the group was successful in their mission, Solo was killed by his son.
Ren later fought Finn in a lightsaber duel, overpowering the former stormtrooper. Ren then attempted to use the Force draw Anakin Skywalker's lightsaber, which Finn had been using, to him, but the weapon instead flew toward Rey. The two were evenly matched at first, but Rey managed to overpower Ren.
During Ren's fight with Rey, Poe Dameron destroyed Starkiller Base's thermal oscillator with his X-wing, causing the planet to disintegrate. First Order leader General Hux contacted Supreme Leader Snoke about the situation. Snoke ordered Ren to be brought to him, so that his training could be completed.