[John’s] form will stand out more distinctly if we but glance at some leading circumstances in his history. He was young, perhaps in his teens, when he entered into public life; and was a Galilæan, son of Zebedee and Salome, and junior brother of James the Great, with whom he pursued the vocation of a fisherman. Like all young men of true and powerful temperament, he was capable of vehement anger, which would occasionally burst forth (Luke 9:51-56). Hence he was surnamed ‘a Son of Thunder.’ When the hour of danger came he never turned his back in the day of battle. Such was John: lowly, yet noble; calm, yet passionate; gentle, yet brave; simple, yet real; in the main, a man to be greatly admired and safely followed.
— James Nisbet’s Commentary