Luke Skywalker: Obi-Wan. Why didn't you tell me? You told me Vader betrayed and murdered my father.

Ben Kenobi: Your father was seduced by the dark side of the Force. He ceased to be Anakin Skywalker and became Darth Vader. When that happened, the good man who was your father was destroyed. So what I told you was true, from a certain point of view.