Darth Vader didn't learn he had a daughter until Return of the Jedi, when he stood before Emperor Palpatine. The Emperor's power probed Luke's mind, attempting to goad him to fall to the dark side, and he discovered Leia's existence.
Vader learned that Leia was his daughter by sensing it from Luke in Return of the Jedi. Vader learned about Luke after he sent Boba to capture Luke alive, but he escaped and Boba only managed to learn his name: Skywalker.
Key details in the Obi-Wan Kenobi series connect to the original Star Wars movies, hinting Darth Vader knew and ignored Leia was his daughter.
In the post-2014 canon universe, the story that reveals Darth Vader discovering Luke Skywalker's identity (and thus the fact that the Death Star's destroyer is his son) is issue 6 of 2015's Star Wars comics by Marvel, which takes place sometime shortly after A New Hope.
He only senses Luke when he actually using the Force, Leia is not actively aware or using the Force and therefore he does not sense her. He is also not looking for a daughter either until Luke spills the psychic beans on her later on.
Before she became a Jedi hunter, she had possession of a droid. However, it was taken away from her, like many of her past belongings and acquaintances. During her time as an Inquisitor, the Third Sister wore black armor with a cape, and wielded a red-bladed Inquisitor lightsaber.
Alderaan's princess knew she had been adopted by Bail and Breha Organa after the Clone Wars, but she had no idea who her parents were. That was until Luke Skywalker told her the truth - that he was the son of Darth Vader, and that she was his sister.
In contrast, Vader was able to sense his personal connection to Luke Skywalker almost immediately. This raises a question as to how he could detect his relationship with one character but not the other. The short answer is that creator George Lucas had no idea Leia would end up becoming Darth Vader's daughter.
It's well known that Star Wars lead characters Luke Skywalker and Princess (now General) Leia are brother and sister. The estranged siblings didn't know about their familial relationship until "Return of the Jedi." They even shared a passionate kiss in the previous movie, "The Empire Strikes Back."
For Leia to name her son Ben Solo is the greatest honor, with Obi-Wan's memory able to live on in someone she loves. It is a sweet and moving gesture, and it retroactively addresses the questions that lingered around the Ben Solo name. After all, why name your child after someone who was important to someone else?
Anakin Skywalker never knew Padmé was pregnant with twins, and he believed his child had died with his wife. He had no idea Padmé had given birth before she died, still less that the Jedi had spirited the children away and hidden them.
Why didnt Obi-Wan tell Vader about Luke and Leia? Because he wasn't Luke's father at that point. Lucas retconed it when making Empire Stikes Back and changed the character of Darth Vader into the fallen Jedi that was once know as Anakin Skywalker.
How does the Third Sister know about Luke and Leia? Reva explained that she discovered a connection between Bail and Obi-Wan in the archives. She doesn't realize that Leia is Vader's daughter. Reva does attempt to use the Force to peer into Leia's mind when she kidnaps her again.
In the main Star Wars timeline, of course, Darth Vader's attempts to resurrect Padmé on Mustafar were doomed to failure. But it's fascinating to speculate what would have happened had he been successful.
Yoda tells Luke in order to fulfil his training and become a Jedi Master he must defeat Darth Vader. Luke asks what would happen if he failed, or died, Yoda mentioned that there was another Skywalker with the force. Luke realises that Leia is his sister, repeats her name and they talk, then Yoda dies.
Over the years since the Youngling massacre, and even sometime before, Darth Vader has regretted killing the Younglings, recognizing that it was the most terrible thing he had ever done.
The Younglings Reminded Anakin of How Different He Was
Those negative emotions also power the dark side, meaning Anakin likely felt stronger as he killed the younglings. That, in turn, reinforced his belief that only the dark side could save Padmé.
While their affection had to remain hidden, the two kept in frequent contact, even throughout the Clone Wars. But despite this, Anakin found out that Padme was pregnant only a couple of weeks before the twins were born. So, why did it take so long for her to tell him?
For the first time in all his life, Darth Vader sees a Jedi act the way he was always told Jedis should act, and seeing his son become the ideal of what the Jedi Order claimed to be made Vader not only love his child, but greatly respect him.
During the Imperial Era, a human female nurse served the Galactic Empire on board the Death Star under the supervision of a doctor. They both served the Sith Lord Darth Vader as his personal medical caretakers. The nurse became obsessed and psychotically in love with the Dark Lord of the Sith.
Although C-3PO is a tell-all, it's possible that he was directly programmed not to say who Leia is. This is something that George Lucas himself suggested in an interview back in the 1970s, which made it into the book The Making of Star Wars: The Definitive Story Behind the Original Film.
George Lucas didn't plan on making Darth Vader the secret father of Luke Skywalker. As much as fans have been told that Lucas had a massive plan for the Star Wars saga prior to 1977, the sources closest to that process say the opposite.
Her first reaction is one of slight revulsion, perhaps even of him. She gets a very concerned look on her face. Then he tells her she's his sister. She says quietly, “I know.
A new Star Wars novel confirms when Emperor Palpatine learned Luke is Darth Vader's son: right before his call with Vader in The Empire Strikes Back. Star Wars reveals Emperor Palpatine learned Luke Skywalker is Darth Vader's son during The Empire Strikes Back.