Easterhay wrote:

I know you all like your little links on this forum

It's the difference between having an opinion, and having an opinion backed up by someone else with a similar thought. Knowledge building.

I can say Admiral Akbar was the other, duh you all should know that. Now go debate you stupid sillies.

What Tobar wrote is predominantly correct:

The only reason they made Luke and Leia sister was to tie up the story into this one trilogy. Originally the "other" Yoda spoke about was supposed to be the star of episodes 7-9 but after ESB Lucas decided to just end it after ROTJ.

Now sure you can say it wasn't the 'only reason' and maybe the decision didn't happen after ESB and back that up with other statements.

Here's Gary Kurtz backing up the overall sentiment:

http://www.filmthreat.com/interviews/8/

So the story was quite a bit more poignant and the ending was the coronation of Leia as the queen of what was left of her people, to take over the royal symbol. That meant she was then isolated from all of the rest and Luke went off then by himself. It was basically a kind of bittersweet ending. She’s not his sister that dropped in to wrap up everything neatly. His sister was someone else way over on the other side of the galaxy and she wasn’t going to show up until the next episode.