Don't need no Qui-Gon. Original script just had Obi-Wan and Obi-Wan actually pretty much acted like Qui-Gon and talked like him. if i remember correctly.
Remember back in ANH Od Ben mentioned Owen not wanting Anakin getting involved with the Clone Wars. Aunt Beru remarked that Luke was not a farmer he had too much of his father him in and Owen was like "that's what I'm afraid of". There was a lot of familiarity there. Maybe they were brothers. why couldn't they be?
Vader would have no reason to go there if he had no knowledge of his offspring. And his brother was of no importance to him.