John's father was Zebedee (Matthew 4:21). He and his brother James were both disciples of Jesus. His mother was apparently the Salome who served Jesus in Galilee and was present at the crucifixion (Mark 15:40-4; Matthew 27:56). She also appears to have been a sister of Mary, the mother of Jesus (John 19:25; Mark 15:40). If this is so, John was Jesus' cousin. Since Jesus and John the Baptist were also cousins, this would also make John a cousin to John the Baptist, whose mother, Elizabeth, was also a close relative of Jesus' mother (Luke 1:36).

On the morning after Jesus' resurrection, John ran with Peter to the empty tomb, and saw the risen Christ walking on the Tiberias shore. With his brother James and the other apostles, he helped establish the first church in Jerusalem, and later served other congregations in Ephesus and Asia Minor.John seems to have worked in partnership with his brother James and his father, Zebedee (Matthew 4:21), as well as Simon Peter (Luke 5:10), and was even an acquaintance of the high priest in Jerusalem (John 18:15-16). He was one of the three disciples of Jesus' inner circle (Mark 5:37; 9:1-9 and 14:33) and was recognised as closest to Jesus. At the last Passover together John is portrayed as leaning on Jesus' chest (John 13:23-25),which is an expression of friendship and brotherly love. Throughout the Gospel he wrote of himself indirectly, referring to himself five times as “the disciple whom Jesus loved" (John 13:23; 19:26; 20:2; John 21:7 and 20).

 As Christ was being put to death by the Roman authorities, John proved fearless, running the  risk of being incarcerated, scourged and crucified for supporting Him in the hour of His greatest need. Before Christ died He put His mother, Mary in John’s care: "Near the cross of Jesus stood his mother… When Jesus saw his mother there, and the disciple whom he loved standing nearby, he said to his mother, ‘Dear woman, here is your son, and to the disciple, ‘Here is your mother.' From that time on, this disciple took her into his home" (John 19:25-27).

John's three letters overflow with statements that help us understand how God's love contrasts with human love. In his first epistle, John gives us the definition of godly love: "For this is the love of God, that we keep His commandments…" (1 John 5:3). John knew the source of godly love, and that God communicates His love through the laws He gives us. God's love is different from the natural love of humans. The Greek verb for God's love, agapao, means a deliberately applied concern for others. A lesser level of love, phileo in the Greek, means a fondness or affection for another person. 

John focused on and taught about godly love as the most important virtue a human being can exhibit: "There is no fear in love; but perfect love casts out fear… We love Him because He first loved us. If someone says, ‘I love God,'and hates his brother, he is a liar; for he who does not love his brother whom he has seen, how can he love God whom he has not seen? And this commandment we have from Him: that he who loves God must love his brother also" (I John 4:18-21). John knew humans can distort the concept of love, but godly love always puts care and concern for the other person first.

During the Christian persecutions under Emperor Domitian (81-96), John was banished to the island of Patmos, in the Aegean Sea. There, some 65 years after Jesus' crucifixion and resurrection, God revealed to John the dark days that lay ahead, which he recorded in the book of Revelation.

Early on in John’s life Jesus nicknamed him a Son of Thunder (Mark 3:17). The Gospels don't explain why, but it could be because John may have originally had a flaring temper. Early in Jesus' ministry, for example, John forbade a stranger to use the name of Christ while casting out demons (Mark 9:38). On another occasion Jesus had to rebuke John for his hotheadedness when he wanted to call down fire from heaven onto a Samaritan village (Luke 9:52-56). 

John's writings, however, reveal he had become a completely different man as he followed in the footsteps of his Master. Hearing Jesus speak of godly love and watching Him practice it among those who didn't appreciate Him could have been what transformed John into one of the three disciples of Jesus' inner circle (Mark 5:37; 9:1-9 and 14:33). John became an Apostle who learned that God is love and reflected that love in his life (1 John 4:8).