I have been preaching a series on the letters to the seven churches in Revelation. I thought you might find this background information on John interesting.
John was the son of Zebedee (a fisherman of Galilee) and his mother's name was Salome, who is believed to be the sister of Mary, Jesus' mother. John, along with his brother, James and the apostle Peter and his brother Andrew, were all partners in a fishing business prior to their call by Jesus to follow Him.
John became the pastor of the church in Ephesus. It is also believed that John founded the churches of Smyrna, Pergamos, Sardis, Philadelphia, Laodicea, and Thyatira. He at least had a special relationship with them.
Whereas John's brother, James, was the first of the apostles to die, John was the last. All of the apostles met a violent martyrs death except John who died peacefully in Ephesus at a ripe old age. Church tradition says that while John was living in Ephesus, he had with him Mary, the mother of Jesus.
While in Ephesus, by order of the Roman emperor Domitian, John was carried to Rome, where he was cast into a cauldron of boiling oil. He escaped by miracle, without injury. Domitian afterwards banished him to the prison island of Patmos, where he wrote the Book of Revelation. Nerva, the successor of Domitian, recalled him. He was able to live the rest of his life and complete his ministry in Ephesus.