Darth Vader cannot tell his offspring solely by being in proximity to them, or even close intimate proximity. He does not realize he is interrogating his own daughter by mind probe, and he doesn’t cotton that his son is on the Death Star, or that his son is about to blow up the Death Star.
Vader knows about Luke before the Emperor contacts him while he is hunting down Han and Leia in the asteroid field. He does not sound surprised when the Emperor says "Luke Skywalker. Further, he knows this Skywalker is “just a boy,” and that the boy had been with Obi-wan Kenobi.
There is a significant period of time between the two films. In this time, Vader would have had plenty of time to gather the available data on the destruction of the Death Star, the activities of Obi-wan Kenobi, and the activities of the rebels. Certainly, he would have tracked the Millenium Falcon backwards to see where it had been engaged in the service of Obi-wan Kenobi. This would lead him to the knowledge that Skywalker had been seen in the bar on Tatooine, etc. etc.
So it’s not a shock he knows the information by Episode V.
This isn’t exactly canon, but I always wondered if the Alliance wasn’t making some PR for their own sake out of Luke around the time of the opening of ESB. Not necessarily a publicity campaign that would make him known throughout the empire, but dropping it around the right circles where people might be willing to support them if they had a bit more confidence that the Rebellion might have a chance.
“Yeah, we’re not saying that he’s been trained in the Jedi ways like the old days, but the Force is strong in him, he’s the son of one of the Jedi heroes of the Pre-Empire days, Anakin Skywalker, and was trained by Obi-Won Kenobi before Kenobi died. He saved Princess Leia from Darth Vader, blew up the Death Star, and personally I feel like he’s just getting started.”
(This is assuming the fact that Anakin Skywalker=Darth Vader is known to very few people.)
The real question is why Obi-Won and Yoda did such a half-assed job at hiding Luke. They put him on Vader’s home planet, with Vaders relatives, and had him keep his last name. Had they just told his uncle to change his name to ‘Luke Lars’, Vader would’ve presumably never figured it out.
Actually, before the prequels made it clear Yoda was trying to hide Luke, I assumed that Vader always knew he had a son (but not daughter), and had just decided to let him be raised by his uncle why he was busy conquering the universe and hunting down Jedi
Actually, it’s kind of brilliant to hide Luke as Vadar’s nephew with in-laws he never visits on some jerkwater planet he probably never plans to go back to.
I mean he knew that Padme was preggers, but that was about it.
In retrospect it was stupid for the crew that separated the twins and hid them from Vader even kept Luke’s last name. Clearly no one was in the know about Leia, cuz she had a different last name, but just think if they made him Luke O’Malley or something like that.
That’s the point. The last he saw of Padme, right before his duel against Obi-Wan on the lava planet, she was pregnant, unconscious, and badly injured. After the cybernetic surgery, Palpatine told him that Padme had died. At that point, he had no reason to believe that Padme had delivered.
But, when he starts hearing about this Skywalker kid who blew up the Death Star, and he puts it together with “the Force is strong in this one”…DUH!
“She may be of some use to us after all.”
“Who are you talking about? The girl you told me to terminate immediately like hours ago? Dude, if you’re going to revisit your decisions like this, you really need to work on your impulse control.”
Actually, aren’t Tarkin and Vader notified of the Falcon’s arrival almost immediately after the termination order? Vader turns around and says “She may yet be of some use to us.” The order never got out of that room.
I have some excuse for being this nerdy, honest. I just watched the movie again last week.
