The funny thing about Lucas allowing it to be done was that it finally put a confirmed by himself lie to his entire claims back in the 70s and 80s about always having a nine part or twelve part film series, and Anakin being Luke and Leia's father, etc.
Starkiller and Skywalker are two separate characters, actually three at the start, Lucas jumbled them up so as to reduce one character from the script and renamed Starkiller to Skywalker. Luke and Leia are definitely never hinted at being related, nor Annikin and Leia. Hell, they don't even meet until the end award ceremony scene.
Had he not trimmed the script, and I read this before about other later versions, it probably would have taken two films to tell this version of The Star Wars. Then he slashed it up after doing
American Graffiti and realizing how much useless fat there was.