I myself agree they were young during our Lord’s ministry, for the most part, with a few obvious exceptions like St. Matthew, who had been a tax collector, and conversely St. John being the youngest, perhaps as young as 13 or 14 when he first joined our Lord, given that according to tradition he wrote the Apocalypse around 90 AD and was the only Apostle to die of old age, and his direct disciples included St. Ignatius and St. Polycarp. This also explains why our Lord assigned the Theotokos as a mother to John, and the physical affection between them, with our Lord being a Father-figure (which is not to say Zebedee was a bad father; we know almost nothing about him, but one can have multiple father figures in childhood in addition to ones actual father).
