Matthew 4:21

‘And going on from there he saw two other brothers, James the son of Zebedee, and John his brother, in the boat with Zebedee their father, mending their nets, and he called them.'

With His two new disciples following him He then walked further along the shore and came to where two other brothers were sitting in their boats with their father mending their nets. And He called them in the same way. Their father was no doubt well aware of their enthusiasm for Jesus and His message, and he seemingly made no effort to stop them. He recognised the inevitable, and probably even rejoiced at heart, for they were seemingly a godly family, even if their mother was, like most mothers, ambitious for her sons (Matthew 20:20). They were indeed quite a prosperous family, for we learn elsewhere that they had hired servants to assist with the fishing (Mark 1:20).

It may be that the mention of their ‘mending their nets' in this case (as with the ‘casting of nets' of Simon and Andrew) is intended to be an indicator of their future work of caring for the people of God.