Hello All,
Wow seems we are getting into a major story debate here so I thought I would weigh in on the subject.
I am no means an expert. So I will first source my information, as the work of Micheal Kaminski in his 600 page book "The secret history of Star Wars". A must read for every SW fan in my opinion.
Sans_Fi you are totally right. The story line was forced and it did not make any sense. It was nothing more than a stop gap for George Lucas to tie up the series in ROTJ. Yes... there was going to be a sequel trilogy. SW was not always the "Tragedy of Darth Vader"
So where did it all go wrong?
George Lucas had a lot of trouble with making ESB (which led to the falling out between him and Gary Kurtz). The project was over budget, Irvin Kershner spent too long on it and went he went in a different creative direction. George didn't like the process and the actors didn't like it much either.
ROTJ comes along, George is in even more trouble. He is going through a messy divorce with Marcia (which crushes lucasfilm financially for 15 years), trouble with the MPAA (Steven Speilburg wanted to direct ROTJ but the MPAA wouldn't let him), the actors are even more tired with the subject matter to the point that Harrison Ford is begging to be killed off, and Richard Marquand was not experienced enough to direct the thing by himself.
So George says.... "wow... another 6 movies. I can't do it. 3 is enough. I have my ranch and that was my goal. " So he decides to wrap it all in ROTJ. So he has to tie up all the loose ends in the story, and end the saga. So he puts the ending of Ep9 in RotJ.
Luke originally was supposed to kill Darth Vader in ROTJ. Then in the Sequel trilogy Luke finds "the other", trains him or her, and they go running off to defeat the Emperor in Episode 9.
So the "other" line served two purposes.
1. It gave the audience a feeling that Luke could fail (and George could conveniently write out Mark Hamil should he wish to leave the project).
2. It was part of the plot to sequel trilogy.
George, wanted to end it all in ROTJ. So rather than just pick a new character out of the air and say "here is the other!" He forced Leia to be Luke's sister and solved the love triangle as well.
So I hope this answers our questions to why it feels forced. However, I am still in favour of the storyline staying the same. It is the way Star Wars was written and should say.
Now, on a side note, to find out who the "other" was going to be, more information on the sequel trilogy, and why it will never be made. You will just have to read "The Secret History of Star Wars."
Matticon.