Why did John identify himself as he did in these verses? Perhaps he did so because this description highlights his intimacy with Jesus. That intimacy was evidently a factor in Jesus" plans for John to which He proceeded to refer ( John 21:22-24). These plans included his writing this Gospel ( John 21:24). Therefore by presenting the writer as an intimate of Jesus, John was establishing his credentials as a reliable eyewitness of what he reported. A second reason may be that this description also reminds the reader of John"s intimacy with Peter. This helps us understand Peter"s question about Jesus" will for John. Peter evidently wanted to know what would happen to his young friend if he himself was going to suffer crucifixion. [source][source][source]
Peter was not the only Christian who wanted to know God"s will for another believer"s life. Many Christians since him have wanted the same information but not always for as altruistic reasons as Peter presumably had. [source][source][source]