JunkMonkey
Lord High Vizier of Nowt
When Lucas did the first film there was no direct inference that Vader was in any way related to Luke . Obi Wan told Luke his father was betrayed and murdered by a young Jedi named Darth Vader . That there tells us that Vader was separate person altogether from Anakin . In an an earlier version of the story which was was adapted as Graphic novel, Vader was not Luke's father at.
I'd always assumed - even from the go - that they were the same. The implication was there. Jekyll and Hyde.