Okay, so by the end of episode 3 Darth is rising to be the right hand man of the emperor meanwhile his wife has twins, dies, and one is sent to grow up under the alias Princess Leia while the other assumes his real last name as Luke Skywalker and hides with his aunt and uncle, all unknown by Vader.
We all know Vader finds out about Leia through the Yoda saying “no, there is another”, Luke asking Ben “Who is this other?”, Ben saying “You have a twin sister”, and then Vader reading Lukes mind during their duel with “So, you have a twin sister, your thoughts have betrayed you.”
But exactly where does Vader find out about Luke being his son??
Does it happen sometime after Luke destroys the deathstar and his name is later in the Rebellion Daily News? And why does he keep the name Skywalker if he’s supposed to be hiding from Vader? And when do we even know Vader is looking for him? Is it when Lando says “he’s looking for someone called, uh, uh, Skywalker”?
And how come the guy who’s been through the whole ordeal (C-3PO) isn’t telling everyone what’s going on, “Obi-Wan! Long time no see”, “Hey, that’s Darth Vader, he built me when I was a kid”, “Skywalker? Luke Skywalker? I think I used to work for your dad.”
It’s established in the opening crawl for Empire Strikes Back that Vader is looking for Luke:
The evil lord Darth Vader,
obsessed with finding young
Skywalker, has dispatched
thousands of remote probes into
the far reaches of space…
So looking back it’s assumed that Vader already knows he’s his son and the Emporer knows it too but they’re coy about saying so when they’re talking to each other so as to not spoil the surprise for us.
Re: C3PO - I’m really hoping they address that in the next movie. My guess is he gets his mind erased. (You forgot 3PO not even remembering he used to live on Tatooine: “What a desolate place this is.”)
We don’t know for sure. However, recall that Vader knew that the kid who blew up the Death Star has some serisou potential (“The force is strong in this one”) We can be sure that the Empire has sources inside the Rebellion. Once he hears that the kid’s name is Luke Skywalker, and that he grew up on Tatooine, it’s not a huge leap to figure out that he’s related. Presumably this happens between Ep IV and Ep V. This also explains Vader’s sense of urgency in hunting down the rebels on Hoth. He knew that in one stroke, he could crush the Rebellion and find his son.
It’s unclear just how much the Emperor knew, and when. Presumably, he knew as much as Vader, and at roughly the same time. I think when Palpatine and Vader were discussing turning Luke, they were already fully aware of who he is and what his heritage is.
This is indeed what happens in the Ep. III graphic novel.
Just in case spoilage is still a concern on this subject:
Infant Leia is sent off with Detective Simone to hide her while she grows to become Carrie Fisher. The droids are given to Captain Antilles (his ship is the one boarded at the opening of Ep. IV), he is ordered to wipe 3PO’s memory. Presumably this is done to preserve the secret of the twins.
The droids are going to be a problem, barring a memory wipe, but I don’t find it too problematic that Anakin knows about Luke. He’s the Dark Lord of the Sith. Is it really that much of a stretch to learn he’s also a deadbeat dad? He doesn’t give a fig about Luke until he witnesses the destruction of the Death Star, then thinks “hey, that’s the fruit of my loins! The issue of my seed!”
