Luke asks her, very much later, if she remembers their mother. He doesn't ask about their father.
Secretly, she is grateful for this. For the truth is that she remembers him very poorly. And none of those fuzzy memories are good ones.
Leia was only three when she and Mama snuck onto the spaceship that was going to see her papa. Only three when she hid in the shadows as Papa hurt Mama. Only three when General Kenobi told her that Papa was dead.
Only three when Uncle Bail—the man she would later call "Father"—told her that something had gone wrong, that she wouldn't be able to meet the little brother-or-sister that she'd been longing for, that Mama, was gone.
The truth is, she never realized Luke was her brother until he told her. In her defense, she thought he was dead.
Of course Vader knew that the Princess of Alderaan was his own daughter. He may not have been able to see the girl as often as he'd have liked when her mother had been alive, but he still knew his daughter's features by heart.
Bail Organa had been one of Padme's closest friends. It didn't surprise him that she had named Organa as Leia's guardian in her will.
And anyway, it wasn't as if the girl's father wasn't legally—and metaphorically—dead. And even if Anakin Skywalker had still existed, it wouldn't have mattered. He'd never had much of a legal claim to the girl. His marriage to her mother was never registered. Leia's birth records listed FATHER as UNKNOWN.
Just as well. Organa was a far better father than he could ever be. A Sith Lord had no business being a parent.
She isn't surprised when he tells her that Vader is her father. The truth is, she's always known.
She never quite connected her papa with with the name "Anakin Skywalker."
She knew he was a Jedi, of course. Mama had told her that when she'd asked why Papa had to be a secret. But she hadn't known Papa was a famous Jedi. Mama never let her watch holovid.
The only name she ever remembered Papa being called was "Annie."
By the time she was old enough to search the records for traces of him, everything related to the Jedi had been expunged. She didn't try again. Bail Organa was her father in all the ways that counted.
The truth is, she hadn't wanted to remember their father at all.
He was a terrible father.
Vader had always known that he would be.
He chopped of his son's hand in a fit of pique. He allowed his daughter to be tortured for the good of the Empire. Vader had done these things knowing who they were. It didn't matter that he regretted those actions. He had done them.
He, Darth Vader.
He really had wanted Luke to join him. Leia was better off where she was—even if it was at the heart of the enemy—but Luke... Luke was different. At least he'd been able to watch Leia grow up from afar. He hadn't even known the boy was alive until he was eighteen.
Of course by then the boy had already wanted to see him dead. So had Leia for that matter
It was fair. He'd wanted to see his own unknown father dead as well. He had no illusions that he wasn't a child of rape. Many slave children were and his mother had never told him anything about his father. He knew what that meant.
He wasn't a rapist. He wasn't his father. But he had murdered his children's mother.
Killing the emperor hardly made up for that, but it was something.
Leia tells Luke that their mother was very beautiful and very sad. She doesn't tell him why she was sad. She doesn't think she needs to.
Some truths are self-evident.