Why would Luke say “…your mother. Your real mother.” if Leia didn’t know she was adopted?
It’s the only reason he reiterates that point!
Sure, the PT throws a few wrenches in that, but that’s problems in the PT, not the OT. I’ve said it often around here lately, but the OT can’t be blamed for inconsistencies created by the PT.
I’m not even thinking about the PT here. Luke says “real mother” because at this point he knows that Leia is his sister, and he also knows that Leia doesn’t know that, so he concludes she must be adopted. I’m just pointing out that if we accept the fact that they’re brother and sister AND Leia’s mom was alive for a few years of her youth, it doesn’t make sense for her to not know she had a brother or for Vader to not know about her. Only way it makes sense is the scenario I mentioned: Vader had a one night stand with Leia’s mother or otherwise ended their “relationship” before he knew she was pregnant. But if that’s the case, why would their mother give up Luke and have him live on Tatooine? Having Leia be Luke’s brother doesn’t make sense and that’s without even considering the PT.