To create a baby, the mother contributes a full set of chromosomes.The father contributes another full set. To form one cell for life to begin, it takes 2 sets. Mary contributed the human chromosomes, but God contributed the divine chromosomes (man was created in His image and likeness so this wasn't cross speciation). The complete cell therefore was both human and divine. The human is the "child born to us." The divine is the "Son given to us in Isaiah 9:6." The Son is the Word who was in the beginning, was with God and was God (Jn. 1:1). That's why He is called "Mighty God." He is called "eternal Father" because you can't have a son without a father. God is the eternally begetting Father who is distinct but not separate from the eternally begotten Son. By the time Jesus was 12, He knew who He was, but as a human who began as a baby, He was not omniscient. He was limited in time and space until after His resurrection.He learned who He was through what His mother told Him, and what He learned from Scripture through the shepherding of His Father.