screams in the void said:
…until that moment , he did not realize it was staring him in the face in form of Leia being his sister . So that was when that plot point came along.
Wait, I thought it was back in 1974 when he was writing the original Darth Vader 6 - 12 - 1 - 9 film Saga (genuflect).
I think it’s weird that Lucas doesn’t seem to think there are people who remember him saying he wrote “no, there is another” before he had any idea of how he was going to address his lack of story regarding that fill-in line.
The truth is out there for people who care enough to take time to look for it.