In the iconic opening sequence of Star Wars: A New Hope, Darth Vader has a tense standoff with Princess Leia. Surprisingly, Vader had no idea that Leia was, in fact, his daughter.
Despite his interrogation of Leia, the Sith Lord still hadn't discovered that he was related to the princess.
In contrast, Vader sensed his connection to Luke Skywalker almost immediately.
So how did Vader quickly sense a connection to one child, but have no clue about the other?
The simple answer is that creator George Lucas didn't decide to make Leia Darth Vader's daughter until after A New Hope was released.
The Star Wars books and comics have attempted to explain this long-standing plot hole. Lucas originally planned for a love triangle between Han Solo, Leia Organa, and Luke Skywalker. However, he ultimately decided to make Luke and Leia brother and sister, which is made clear in the way they interact with each other in later films.
Vader didn't actually become Luke's father until Lucas realized the character was a hit with audiences. He improvised many plot elements while writing the original trilogy, so other writers had to find reasonable explanations for the loopholes that came with this approach.
Didn't Vader know Leia was a daughter?
In the canonical young adult novel Star Wars: Princesses, Scoundrels, and Farm Boys, published in 2015, author Alexandra Bracken depicts Darth Vader sensing the Force in Leia during his interrogation in A New Hope. Leia resists Imperial probes, showing her sensitivity to the Force.
This shocks Vader because before A New Hope, he and Darth Sidious were believed to be the only Force users left in the galaxy. Furthermore, the Emperor misled Vader into believing that his children died with Padmé. In addition, they both believed that Obi-Wan and Yoda were long dead.
Unlike Luke, a powerful Force user, Leia's Force abilities are more instinctive and passive. In the original trilogy, Leia never uses the Force in combat, nor does she wield a lightsaber.
It was in the controversial sequel, Star Wars: The Last Jedi, that Leia was first depicted as a character who used the Force, which was an eye-opener for audiences, and the scene where she reached out to save herself from being swallowed by the vacuum of space is still memorable to this day.
Leia's Force Powers Prevented Discovery
Even when she first met Darth Vader, Leia was not particularly aware of her connection to the Force. Leia grew up as a princess on Alderaan and later became a senator on Coruscant. Her adoptive father, Bail Organa, did everything in his power to protect Leia's true identity from being discovered.
In fact, the Star Wars "Legends" story suggests that Leia exhibited Force abilities at a young age, but she did not further develop these powers due to her isolation from the Force and the Jedi. However, this did not affect Leia's choice not to pursue these abilities because she did not want to become a Jedi. She followed her adoptive father into politics and became a prominent member of the Senate at a young age.
The 2007 novel Death Star further explains Darth Vader's failure to recognize Leia. In the novel, Vader senses something familiar while interrogating Leia. Vader even notices Leia's beauty and is struck by her resemblance to Padmé. In the Star Wars comics, Leia is depicted as having a stronger connection to Padmé than Anakin. This explains why she was more prominent in the Senate, but not in the use of the Force.
In Death Star, it seems that the Sith Lord might have discovered Leia's true identity if he had followed his intuition. However, Leia's determination during Vader's interrogation ruined his chances of discovering that she was his daughter.
While this explanation isn't as satisfying as the relationship Lucas had planned from the beginning, it still rationalizes Vader's lack of recognition of Leia.
Reasons for Leia's Caution
Leia didn't realize her Force potential until Return of the Jedi, but that doesn't mean she lacked those instincts or hadn't used them. The series suggests that these instincts played a huge role in her political acumen, explaining how she (like her mother) was able to hold high office at a young age, as well as her extraordinary insight. (For example, she spotted Lando Calrissian's betrayal before anyone else in The Empire Strikes Back.)
In the Obi-Wan Kenobi episode, young Leia is depicted as a very precocious child, already able to bypass the family's servants and catch her adoptive mother off guard on multiple occasions. This was before she was taken hostage and needed to be rescued by Obi-Wan Kenobi.
This event undoubtedly opened her eyes to the reality of her struggle with the Empire and matured her early, helping her become a strong politician.
It may also have taught her caution, which could easily translate into a subconscious repression of her Force abilities. Her Force abilities were already weak—easily dismissed by herself as “good instincts” or something like that—and the early trauma of Obi-Wan Kenobi taught her the wisdom of caution.
It’s not hard to believe that her abilities were repressed enough that Vader could not detect them.
Vader Can’t Believe the Child is Alive
Perhaps the strongest factor in Darth Vader’s failure to perceive that Leia Organa was his daughter was his own denial. Darth Vader simply couldn’t bring himself to believe that Anakin Skywalker’s child was still alive.
Anakin Skywalker’s fall into Darth Vader at the end of the Clone Wars was dramatic and complete, leaving almost no trace of the former Jedi.
By the time of the events of A New Hope, Vader had been so completely consumed by Anakin that he couldn’t even bear the thought of his child still being alive after Padmé’s death.
To believe even for a moment that some remnant of Anakin Skywalker still existed would render all the horrific acts he’d committed over the past two decades meaningless, and Vader simply couldn’t bear the thought.
After everything he had done - killing Mace Windu, slaughtering the Padawans in the Jedi Temple, and countless atrocities committed in the years leading up to A New Hope - the moral reckoning would have been too much for him to bear.
As a result, he chose to follow the Sith Lord even more firmly.
Vader's Attitude Towards Leia Reveals the Truth
As viewers know, Vader betrayed and killed the Sith Lord and saved the entire galaxy soon after reconnecting with his son and learning that Leia was his daughter. The survival of Anakin Skywalker's children propelled the once-great Jedi Knight back to heroism.
Seeing Luke and knowing Leia existed gave Vader the hope he had lacked for so long - the hope he had always refused to acknowledge to himself for fear of getting hurt again. Vader's denial kept him from facing this truth for years - but even he couldn't escape the truth about Luke and Leia.
This was especially evident in his final duel with Luke. Once he knew Leia was still alive, he taunted her about the possibility of leading her to the dark side, which angered Luke enough to finally defeat Vader in combat.
The Sith Lord then tried to kill Luke, and almost succeeded, but Vader eventually broke free and saved his son. Learning Leia's origins and the possibility of what the Sith Lord would do to her played a large role in that decision.
Darth Vader's failure to realize that Leia Organa was his daughter during the events of A New Hope initially seemed like a plot hole, but it actually revealed his deep inner turmoil. George Lucas also didn't know the truth about Leia's origins at first, but it did make for a nice twist for both her and Darth Vader's characters.
（Above images are from the internet）
