uhhhh I will argue with you on that one, all the johns were the same, he wrote Revelation after he was exiled to Patmos and he was VERY old, He is believed to have outlived the other apostles.
Just one of the many places that you can find where it says it is the same John
John is traditionally held to be the author of five books of the New Testament, including the Gospel of John.
http://www.answers.com/topic/john-the-apostle