I understand that Leia being Luke’s sister was a really bad decision. Ok, I got it that GL didn’t want to make more Star Wars movies as he intended to, and there wouldn’t be an explanation for the “other” as he intended if he didn’t go for the Leia’s solution.

So what? I would leave this as a mystery. People would argue for years who the “other” was, and if I were GL, I would never give any hint about it. It would also be like: “Is Deckard a replicant or not”? “Would the “other” be related to Skywalker family or not?” “Will the mystery be solved in a new movie if GL ever decides to do it?” There would be novels that would try to explain who the other was, but there would be never an official explanation.

Not only that would not screw things up with Leia and Luke characters, but it would make the history more appealing by leaving things to people’s imagination. But GL decided to destroy his own creation. He’s not much as a writer I guess.