All the universe-shrinking, story-shrinking plot twists (Father Vader, sister Leia, etc) were invented later, on the fly.
Lucas can't seem to grasp the fact that many of us were there in the 70s. We remember what he said, we remember what was written, we remember what we saw.
http://secrethistoryofstarwars.com – Give it a read George. Maybe it will jog your memory.