I know this is completely illogical to the OT, but at the end of the Episode III video game, Obi-Wan misses Anikin after the "I have the high ground now" part and Anikin thrusts his blade through Obi-Wan's torso, thus killing Obi-Wan and keeping himself from being placed in the Vader Suit. He then continues to meet Palpatine, where he is given his new red lightsaber, and directly after, the following happens: Palpatine: The galaxy is ours now. Palpatine hands Anikin his new saber. Palpatine: Your new weapon, Lord Vader. Anikin then ignites his saber and kills Palpatine. Anikin: No! The Galaxy belongs to me! If all this had happened, then there might not be a Luke or Leia, because Padme might not have gotten off of Mustafar alive. This would also mean that if Luke actually did exist, then there would be no Obi-Wan to teach him and he might not have been taken to Tatooine. I do think, however, that there could be an alternate universe where all this happened. It would be interesting if someone made books out of this idea.