Negative 1 when Splinter of the Mind's Eye was released in 1978 Luke Skywalker was not Leia's brother or darth vaders son. Darth Vader was the man who murdered luke's father and Leia was a love interest.
Lucas states an inaccuracy when he says Vader was always Luke's Father, the story was always about the downfall and redemption of anakin skywalker etc.
An author is allowed to change his mind mid stream about where a story should go but don't fabricate this great mythology over vader that never existed prior to Return of the Jedi or the prequels.
The concept of twins did exist in an earlier draft but Luke Had a brother Deak Starkiller not Leia, also the Leia of the films may be like the female Luke in one of the drafts.
MidiClorians is a too much Like a Regression Back to the third draft where they had the Kiber Crystal to explain and quanitify the force, and use it as a throw way mcguffin.
It was a very lazy ripoff of the one ring of power from the lord of the rings the so called "numinous" object. It was also ripped off of the lens from the lensman novels.
Instead at Gary Kurtz suggestion Lucas made the force more mysterious and ethereal, and quasi spirtual.
Nevermind that the force is probably a reference to Jack Kirby's New Gods The Source, LOL.
I have always understood that the Jedi were always meant to be demigods, I mean the Name Luke Skywalker literally "the one who walks the sky" sounds Like myth to me.
Lucas must have known that all the heroes of greek and roman mythology were demi gods. Thus you had Perseus the son of Zeus and the Gorgon Slayer, Hercules the strongest man on earth and also the son of Zeus, and Theseus the son of poseidon the Giant slayer and minotaur killer.
From the story synopsis for The Star Wars
"After the ceremony is over, and the festivities have ended, the drunken bureaucrats stagger down an empty street arm in arm realizing that they have been adventuring with demigods."