Only Thomas was a disciple of Jesus.
Luke and Jon were the names of writers of the gospels, all of which were written over a hundred years after the supposed death of some random dude there's no evidence ever existed.
No evidence except for having four biographies written about him, or being referenced by contemporary sources like Josephus, or spawning an entire belief system. People can choose to believe anything they want about the religion itself but to think that the person never existed would require the assumption that Caesar, Genghis Khan, Plato, etc. were mythical figures as well seeing as the evidence for their existence is even less comprehensive.
Also, the writer of the book of John was the disciple John, as he referenced himself in the book, and the earliest extant manuscript fragments place it's authorship within the lifetime of Jesus' contemporaries.