Ben Solo was the Grandson of Darth Vader. His parents, Han Solo and Leia Organa, were concerned about the effect such a relationship might have on his future, and asked Luke Skywalker to train him as a Jedi. Supreme Leader Snoke sensed his potential and lured him to the dark side of the force. This led to a confrontation between Ben and Luke. Ben defeated Luke, destroyed the training facility, took the name Kylo Ren, and became a high ranking member of the First Order. Continuing his training under Snoke, he was constantly torn between the dark and light sides of the force. He killed his father Han in an attempt to rid himself of the light.

            He crossed paths several times with Rey, and tried to lure her to the dark side while she tried to bring him back to the light. During one such meeting Kylo killed Leader Snoke and took control of the First Order. 

            This was all part of the overall plan of Darth Sidious. The former emperor of the galaxy was secretly rebuilding the Sith Empire and using Kylo to put the pieces in place. During his last confrontation with Rey, Leia sacrificed herself in one last attempt to sway him back to the light. Kylo was defeated, redeemed, and as Ben Solo helped Rey defeat Sidious and the Sith forever.