How we cite our quotes: All quotations are from Star Wars: The Empire Strikes Back.
Quote #7
VADER: Join me, and together we can rule the galaxy as father and son. Come with me. It is the only way.
This makes us feel like Darth Vader cares about Luke more than he wants to admit. In this interpretation, Vader isn't trying to turn Luke to the dark side to protect the Emperor or defeat the Rebels—he's doing it so he can reunite with his son.
Quote #8
LEIA: Luke...We've got to go back.
LANDO: What?
LEIA: I know where Luke is.
For context, Luke has just telepathically contacted Leia so she can rescue him. This is the film's second subtle hint that these two almost-lovers are siblings, which is explored further in Return of the Jedi.
Quote #9
[Luke and Vader are on different ships communicating telepathically.]
VADER: Luke.
LUKE: Father.
VADER: Son, come with me.
What you can't hear in these transcribed lines is Luke's tone of voice: He sounds eager, almost longing. He feels conflicting emotions towards Vader/Anakin because his entire self-image has been built around a false (or, at least, incomplete) image of his father.