George attempting to claim the Saga was always the story of Darth Vader…
‘Creating The Galaxy: Myth Maker And Jedi Master George Lucas In His Own Words’, by Amy Longsdorf. : OT.com Thread
GL: “It’s really a story about Darth Vader. Luke and Leia became central figures and had a strong impact. But I knew if I gave Darth Vader his due, you would understand what a tragic story the whole thing was and it would change the way you look at the other movies. So that’s why I did it.”
And this screenshot below - from this June 2005 interview with Rolling Stone - George Lucas and the Cult of Darth Vader:-

Also, George is on record claiming that the 6-film Star Wars Saga was always meant to be “the tragedy of Darth Vader”:-
‘Making Sith was a piece of cake’ - a 2005 interview with the London Standard. A screenshot of the quote from George:-

GL: “Originally, Star Wars was intended to be one movie - it was designed to be the tragedy of Darth Vader.”
Yet we know from early scripts and annotated screenplays this was not the case. Vader and Luke’s father are indeed two separate characters in early drafts and scripts - even in Leigh Brackett’s 1978’s draft script for Empire Strikes Back… Anakin Skywalker and Darth Vader are written as two completely separate characters:-
The Empire Strikes Back – First Draft by Leigh Brackett (1978) - from the ‘Starkiller: The Jedi Bendu Script Site’.
In fact, at the very start of the process for George writing Star Wars back in the 1973… there is no mention of Vader at all. Though there is frequent mentions of a Luke Skywalker:-
The Star Wars (Story Synopsis) (May 1973) - from the ‘Starkiller: The Jedi Bendu Script Site’.
The very first mention of Vader, ‘General Vader’ (a ranking officer in the Empire, but is not a Jedi or a Sith, has no force abilities - and is very different character… before being seemingly merged with three/four other characters written around that time… to eventually become the Vader we recognise from the 1977 film), appears in the May of 1974 - in the Rough Draft of The Star Wars:-
The Star Wars – Rough Draft (May 1974) - from the ‘Starkiller: The Jedi Bendu Script Site’.
George is also on record, in 1977, in his private backstory notes:-
“When the Jedi tried to restore order, Darth Vader was still one of the Jedi. What he would do is catch the Jedi off-guard and, using his knowledge of the Force, he would kill the Jedi without them realizing what was happening. They trusted him and they didn’t realize he was the murderer who was decimating their ranks. At the height of the Jedi, there were several hundred thousand. At the time of the Rebellion, most of them were killed. The Emperor had some strong forces rally behind him, as well, in terms of the army and the Imperial forces that he’d been building up secretly. The Jedi were so outnumbered that they fled and were tracked down. They tried to regroup, but they were eventually massacred by one of the special elite forces led by Darth Vader. Eventually, only a few, including Ben and Luke’s father, were left. Luke’s father is named Annikin.”
^ from JW Rinzler’s 2007 ‘Making Of Star Wars’ book, Page 352. (Not, as sometimes mis-attributed to, the 1977 Rolling Stone article)
Also contrary to George’s claims, in 1976 - George Lucas, author Alan Dean Foster & Star Wars publicist & advertising guru Charles Lippincott - when talking about a sequel film that would become the ‘Splinter Of The Mind’s Eye’ novel…

GL: “The other thing we haven’t dealt with is Darth Vader. But Darth Vader, as we discovered in this picture, tends to be pushy; he’s not strong enough as the villain to hold the villain role. he doesn’t have the persona that you need. You really need a Cushing guy, a really slimy, ugly….”
(As already listed in this thread - we know that Anakin Skywalker and Darth Vader were two entirely separate characters… until being retconned in Empire Strikes Back.)
^ The above info (screenshot and text) is taken from the Star Wars Splinter Of The Mind’s Eye Story Conference article - at the Cinetropolis website.
Lucas now claims the 6 Star Wars films ‘form the biography of Vader’… but that he wasn’t aware of this “until 1998”…
A screenshot of a 2005 Vanity Fair article (February issue) promoting Revenge Of The Sith:-

^ ‘Taken as a whole, the six Star Wars movies form the biography of Darth Vader — something Lucas claims he wasn’t consciously aware of “until 1998.”’
George’s own scripts & story synopsis state it is Luke Skywalker - along with novelisations of the film…
Many of the draft scripts for Star Wars were titled ‘Star Wars: The Adventures of Luke Starkiller’ too (before Luke was given the surname ‘Skywalker’ instead), which would seem to confirm the story being about Luke, as can be found at the link below:-
Starkiller - The Jedi Bendu Script Site

There is also no mention of Darth Vader at all in the earlier 1973 Story Synopsis - yet a version of the character of Luke features prominently, which can be found at:-
Starkiller - The Jedi Bendu Script Site
Officially released Star Wars novelisations also referred to the ‘Adventures Of Luke Skywalker’ too…

‘Star Wars: From the Adventures of Luke Skywalker’ - archived StarWars•com website link to the novelisation of the film
‘Star Wars: From the Adventures of Luke Skywalker’ - Wikipedia page (for additional info)
As well as officially released record and cassettes for The Empire Strikes Back too…

The Empire Strikes Back - From the Adventures Of Luke Skywalker - vinyl & cassette cover info at the Restraining Bolt website
Even tie-in Star Wars books focusing on other characters - from the wider Star Wars saga / universe - also had the subtitle of…
‘From The Adventures Of Luke Skywalker’

^ Brian Daley’s two books from 1987 (reprints?) 1979 & 1980 (thank you for the correction, Pakka) - ‘Han Solo’s Revenge’ & ‘Han Solo at Star’s End’.
Even the novel covers for Star Wars carried ‘From the Adventures of Luke Skywalker’ blurb on them in the mid-to-late 1990’s:-

^ note the ‘Formerly titled: Star Wars: From the Adventures of Luke Skywalker’ for the 1997 & 2004 Special Edition Trilogy books.
More information can also be found in this article up on the official Star Wars website - ‘Check out over 40 years of Star Wars: A New Hope novelisation covers’.
Even Lucas himself stated that the Star Wars Saga was essentially about Luke Skywalker’s destiny and his past - when creating ideas for the Empire Strikes Back…

^ a screenshot taken from Page 15 of JW Rinzler’s ‘Making Of Empire Strikes Back’ book.
^ Category ‘#5 • Vader: ‘Luke, originally I was NOT your father’ (Anakin & Vader were two entirely separate characters; until 1978’s ESB 2nd draft)’ of the ‘George Lucas: Star Wars Creator, Unreliable Narrator & Time Travelling Revisionist…’ thread may be of interest.
As is Phil Szostak, Lucasfilm Creative Art Manager & author, in his 2019 “Star Wars Mythbusting” twitter thread…
“Darth Vader wasn’t Luke’s father until the second draft of Empire Strikes Back in April 1978.”
^ twitter.com/PhilSzostak/status/1161026961444990976 + threadreaderapp.com/thread/1157776507533582336.html