Hardcore Legend said:
Once you know Vader is Luke’s father, you look back and see that everything Vader does in ESB and ROTJ is to be reunited with his son.

I know RotJ changed the character of Vader but I can’t really see TESB Vader torturing Han as “attempting to be reunited with his son”. I may be wrong but in my eyes TESB Vader was clearly written as someone who merely wants to use Luke as a weapon against the Emperor. He may have some feelings but he wouldn’t put Luke above his own quest for ultimate power.