Perhaps Leia's Force sensitivity allowed her to form memories even at such a young age. Leia's Force sensitivity is more personal and emotional than Luke's; her first hint of Force ability, in "Episode V: The Empire Strikes Back," is sensing Luke on Bespin.
With Leia's strong connection to the Force, it seems like the most likely solution to this inconsistency is that she's caught glimpses of her mother through Force visions.
The reason Leia likely remembers Padmé is that she could sense her mother's emotions at the time of the senator's passing. Luke didn't possess the same ability as his sister and inherited their father's Force potential. This links with Luke's desire to follow Anakin's Jedi path.
it is likely that her force sensitivity allowed her to “remember” her mother the way she was. Leia's Force sensitivity was always more mental (persuasion,seeing through lies) than it was physical (telekinesis). But as a Skywalker she was a very powerful force sensitive even if she never tapped in to her abilities.
What did Luke Skywalker know about his mother? Most likely? Nothing, until the original trilogy is complete. Luke was raised by the Lars family on Tattooine, and they likely had no idea that Padme was Luke's mother, so he wouldn't either.
Darth Vader found out that Luke was his son through Boba Fett, who revealed to him that the name of the Rebel that destroyed the Death Star was Luke Skywalker. That was when Darth Vader put the pieces together and discovered that this boy, unusually strong in the Force, was actually his son.
Vader was hunting down the pilot who blew up the Death Star, and hired Boba Fett to find them. Boba was unable to, but he did give Vader a name: “Skywalker.” This, combined with his knowing Luke was Force-sensitive and had been trained by Obi-Wan, was what made him realize the truth.
Leia is annoyed with Han, who insists she has feelings for him, so she kisses Luke to prove she doesn't. Presumably, the scene was simply meant to make Han jealous.
However, Leia's strong-mindedness during Vader's probe denied him the opportunity to discover she was his daughter. That serves to justify Vader's lack of awareness of his connection to Leia, although, perhaps, not as satisfyingly as if Lucas had planned for the relationship from the beginning.
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. "Sister," the Emperor taunted.
No evidence would suggest that Darth Vader knew that Leia Organa was his daughter the entire time. However, in the final battle with Luke Skywalker, he learned that Luke had a sister. But the important part is that it was never shown that Vader found out that this sister was Leia.
In "Episode VI: Return of the Jedi," Luke asks Leia if she remembers her real mother. Leia replies that her mother died when she was very young, but she was "very beautiful.
Leia's journey yields a time dilation of 62.6 days; however Luke experiences a time dilation of 700.8 days (1.92 years). The students concluded that Luke is therefore 1.75 years younger than Leia, possibly rendering them the first twins ever to have over a year between their ages.
But when Leia admitted she knew her son was gone, Luke told her that “no one's really gone.” As brother and sister touched, Leia understood that Luke wasn't physically there, but a Force projection. His confrontation with Kylo bought the Resistance time to escape Crait, with Poe taking charge.
Yoda spilled the beans about Luke having a lost relative before he died. Obi-Wan's ghost would later confirm it as Luke's twin sister. Luke himself quickly realize it's Leia after the subtle clues Obi-Wan mentions to him.
Luke and Leia only discovered they were twins in Return of the Jedi despite being Force-sensitive.
This is not because the Third Sister knows that Leia is Anakin Skywalker's child; it is because the Third Sister found a link between Obi-Wan and Bail Organa and she believed Obi-Wan would do anything to save Bail's daughter.
However, she chose not to tell Anakin, presumably because he was about to go into a battle. Anakin was prone to letting his emotions affect him, and knowing that Padme was pregnant would've thrown him completely off the task. And Padme probably didn't think that her husband would be fighting battles for months to come.
After Leia and Luke's lips lock in Lannister love, our wookie friend vocalizes what seems to be his approval. However in hindsight, Chewie was more than likely saying “Your species' obsession with sibling mating is a curious one, I've seen your browser histories”.
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."
A callback to their classic exchange in The Empire Strikes Back, but reversed to great effect. Han, worried that Leia is injured, is relieved when she's okay -- and finally utters the words, "I love you," when she reveals she has a blaster. The princess replies, "I know," before shooting two Stormtroopers.
R2-D2 was present when Padmé gave birth to Leia and Luke, so he knew Luke was Anakin's son – but what he didn't know was that Anakin became Darth Vader. In addition to that, Anakin's fall was surely a painful event in R2-D2's life, one that he definitely wouldn't like to remember or even talk about.
Yoda. Yoda's knowledge of Luke Skywalker's true parentage was also confirmed in Return of the Jedi. As with Obi-Wan, Yoda believed that Anakin's fall to the dark side made him unsalvageable, with the Darth Vader persona being his only identity following his ascension to Sith Lordship.