| Well, His mum knew from the beginning that He was important. And the Bible indicates that she was still around at the time of the main events of Jesus' life. So it's probably pretty safe to assume that she might have filled some of that information in. There was also James, if we are to assume that he was Jesus' half brother.
I honestly don't know on the second one. Obviously, there wasn't anything important or it would've made it in. Maybe He was studying or coming to grips with who He was and what He had to do. Something like that could be cause for serious introspection.
On the third...*shrugs* 
Place me like a seal over your heart, like a seal on your arm; for love is as strong as death, its jealousy unyielding as the grave. It burns like blazing fire, like a mighty flame. -- Song 8:6 |