Many years ago in galactic history, there were Jedi Knights. Hundreds of them, all keeping the peace and protecting the Old Republic. Vader and Palpatine put an end to that, but not a permanent one. There were Jedi descendants scattered throughout the galaxy, and also Jedi Masters such as Yoda and Obi-Wan. But all the descendants either did not know about their hidden power, or were too scared to use it. But Yoda and Ben knew how to use their powers, knew how to control them, and were not scared to use them. They did not use them against Palpatine because they were too scared, but because they knew that a young boy would learn the ways of the Force, like his father before him, and use it to destroy Palpatine. This was not because he knew he had the ability needed in the Force, but because it was his destiny.
Luke had grown up on Tatooine, under the watchful eyes of his Uncle Owen and Aunt Beru. But they weren't his real aunt and uncle. They were merely foster parents, who had decided to raise him as a nephew. Owen was Obi-Wan's brother, who had saved Luke from his father Anakin. Ben had asked Owen to take Luke in, and keep him safe until the time was right for Luke to face his destiny. Having never known his true heritage, the son of Skywalker dreamed of flying in space, of dogfights with fast starfighters. He wanted to join the Imperial Academy, along with his good friend Biggs, but his Uncle Owen said that Luke was needed on the farm. And then one day two droids came along in a Jawa sandcrawler, and were sold to the Lars family. They would mark the beginning of a new chapter in Luke's life, one that would lead him to great things, and horrific revelations. The two droids were of course Threepio and Artoo, who were on a mission to find Ben Kenobi, well Artoo was anyway. Threepio was just there because his did not want to get melted down by the Empire or the Jawas. At the Lars' home, Luke found the holorecording of Leia, in which she asked for the help of General Kenobi. No-one had any idea who he was, but Luke thought she might mean Ben Kenobi. It turned out that she did. Artoo had run off and found Ben.
At Ben's home, Luke was presented with his father's lightsaber. It was his first one, but not his last. Over the time that followed, Luke grew immensely strong in the Force. When Ben was killed by Vader, Yoda took over the young Jedi's tuition on Dagobah. It was while on Dagobah that Luke first realised what he may become should he follow the Dark path. He entered a cave, whereupon he met Darth Vader. Their lightsabers flashed brilliantly in the gloom of the cave, especially when they clashed. But although Vader was more powerful, Luke sweeped with his saber and sliced off the Dark Lord's head. When the mask landed on the ground it exploded, only to reveal Luke's own face beneath the mask. This experience shook him considerably, and here he realised his deepest fears, and that he would have to overcome them to meet his destiny. The legacy of Skywalker would continue in Luke. Anakin had been strong in the Force, and now his son was. The circle was almost complete. Vader thought it complete on Bespin, when they duelled in the carbon freezing chamber of Cloud City. There Luke proved that he was indeed a worthy Jedi, and would not give into the Dark Side. It was also on Cloud City that Vader sliced off his son's hand, and then told Luke of his true heritage.
Unlike most people, Luke could usually see the character of a person just by glancing at them. That is how he knew that there was still good in Vader, his father. On the second Death Star, father and son fought a second vicious duel, one in which Luke severed his father's hand, but could not bring himself to destroy him. On board that monstrous battle station, Luke completed his destiny, and father and son helped each other to a new beginning, a beginning in which Vader died, but Anakin's spirit lived.
In the years after these events, Luke lost contact with Ben, who had been his spiritual guide for so long. Ben told him that the distances between them were too far apart, but one day they would be together. One day Luke would make that journey to the beyond, to where so many past Jedi had been sent before, to where many more would go in later years. Luke was not the last of the old Jedi, but the start of the new. He set up a Jedi Academy on Yavin, where people with potential in the Force could train. Even Leia's children were sent there. From this a new order of Jedi would be forged, and this time there would be no Vader or Palpatine to hunt them down.
Then again, who's to say there won't be? There is always some evil in the galaxy, and sometimes even dead evil can come back to life. The Jedi will never be totally safe from the likes of the Emperor, but then, who is?
Time passed, and Luke found that he needed a soulmate. On board an Imperial ship, he found one. Her name was Callista, and she was trapped inside a computer. When one of Luke's pupils sacrificed herself to destroy the ship, Callista's spirit was freed and passed into the pupil's body. Callista was much older than Luke, and so she had much more experience. She was also a Jedi, and could pass on many things to the students and to Luke himself. But the transition to the body had not allowed Callista to possess her Jedi skills. She was now completely powerless, but she and Luke vowed to find a way for her to regain her former glory. They became very close, and even spoke of children, but then one day Callista left. She did not say where she went, but Luke went in search of her. When he did find her, she told him that they could not be together. Any children they might have may not be Jedi, and that would be a terrible loss to the galaxy, because rightfully the offspring of Luke should be very powerful Force users. There was nothing the Jedi Master could do. He had to let her go, though it pained him greatly. Since then Luke has not found anyone else. Leia has had three children, and it may be possible that these kids are the only offspring from the Skywalker twins.
Having been through so much over the years, and been alone for so long, it is possible that fate will not allow Luke to find someone. This may be his true destiny.