Vader never know that Princess Leia was his daughter till after his death and redemption. There was no evidence backing it up which was why he never knew. It was why he never got into any kind of relationship with her.I used to write fanfics about the father and the daughter. Instead of Luke and Vader, what if he's known that Leia is his daughter as he's about to probe her?
Which is a shame, because the things he's done to her as her Father, I bet her does feel very remorseful after his death and redemption.Vader never know that Princess Leia was his daughter till after his death and redemption. There was no evidence backing it up which was why he never knew. It was why he never got into any kind of relationship with her.