which famous guitarist is the one that began playing guitar the latest? i.e steve vai 13
It was Paul McCartney. He only learned to play the guitar when he was 75.

"I don't have an instrument, I don't have a great voice, I just have some nice clothes maybe." paul rutherford
Glenn Tipton from Judas Priest was about 20 years old when he took up guitar. His mother taught him to play the piano before that so there was some musical background. That is the oldest that I had heard of.