There is a bit of a disconnect, is there not, between the Virgin Birth as reported in two gospels, his family's puzzlement at the answer he gave at the age of 12 (Luke 2:49), and Mark 3:21 ("He is out of his mind")? It is perfectly reasonable to be curious about and to speculate about this disconnect. One possibility: The Virgin Birth accounts and the incident at the age of 12 are pious inventions, and Jesus basically burst on the scene at the age of 30 or thereabouts. The missing years of Jesus are indeed a mystery. Even if they were spent as simply a local carpenter, the utter silence of the gospels is puzzling. My guess is that the years prior to 30 were understood to be simply unimportant - the Jesus who is important is the one who burst on the scene at the age of 30. He may well have had a growing awareness or even sudden revelation as to what his mission was.