Well remember when Jesus was 12 years old and Jesus tarried behind in Jerusalem, and that Mary and Joseph searched for him and found him in the temple teaching, and they told Him they had been looking for Him in sorrow, and Jesus told them this, "How is it that ye sought me? wist ye not that I must be about my Fathers business?" Key in on that, 12 year old Jesus knew God was the Father, so He knew even then He was the Son of God.