Tobar said:

Star Wars Purist said:

You are right. The dialogue from Star Wars (and Return of the Jedi) suggests that Luke's father/Anakin and Ben/Obi were equals rather than master-apprentice.

BEN: A young Jedi named Darth Vader, who was a pupil of mine until he turned to evil, helped the Empire hunt down and destroy the Jedi Knights. He betrayed and murdered your father. Now the Jedi are all but extinct. Vader was seduced by the dark side of the Force.

Before ESB, this line was only talking about Vader, not Luke's father.

When Lucas wrote that dialogue, Vader and Luke's father were two separate people. When Alec Guinness performed that dialogue, Vader and Luke's father were two separate people. When audiences first heard that dialogue, Vader and Luke's father were two separate people. Until Lucas wrote the second draft of ESB in 1978, Darth Vader was not Luke's father. Between then and April 12, 1980 (when the novelization was released), Luke's father and Darth Vader were still officially two separate people.