Did Vader ever find out she was his kid? I haven’t seen the OG movies in many years so I don’t remember
In RotJ, when Luke fights him on the Super Star Destroyer in front of Palpatine, doesn't Vader read his thoughts? I definitely remember Vader saying, 'Sister ....' I haven't watched the OG trilogy in years too though.
It's been a while, but I'm pretty sure Luke and Leia had a talk about being siblings before she told Han. It was equally weird where Leia just knows, but it happened.
What are you talking about? Obi-Wan shows up as a Force ghost after Yoda dies and helps Luke realize Leia is his sister. Then, before leaving the Ewok story time to surrender to Vader, Luke tells Leia that she's his sister.
Then she tells Han after the battle of Endor is over. It's pretty clear how that info was generated and passed between characters in a non-story busting way.
That's....an extremely important part of Return of the Jedi. It's like saying you don't remember the part where Darth Vader reveals that he's Luke's father.