For the first four years of his life, Dean Winchester had a great childhood. Two loving parents and living in a small, safe town. Nothing could touch him. Especially since unknown to anyone he had a guardian archangel protecting him. Keeping him safe from anything that could hurt him.
Save for what was needed to motive his destiny, such as when Azazel came into his home and killed his mother. Forever changing his life and taking away his innocence. After that night, his dad made him Sam's caregiver. Completely taking away any chance of a childhood. After that night Dean was becoming the soldier that his dad wanted. And his mom never wanted. She had been a hunter before she met John. She had known of demons and everything else that dwelled in the night. As her parents had been hunters and back for centuries. Generations of her family had for centuries protected the Earth from evil. For her family were Protectors. Guardians of the Earth.
For her family was cultivated for the birth of the Sword. The Protector of Mankind. The Destroyer of Evil. And most importantly, the Shield of the Death Guardian and the Knight. Dean was the Shield, he was also the Vessel of Michael, Michael's Sword. Or he was suppose to be. Somethings can be changed after all.
After he was four, Dean became the Soldier and nothing more, his father saw to that. Stripping him of everything but the need to protect and 'serve'. Sam on the other hand wanted more. So when he turned eighteen, he left. It would be years before the brother met again. During the time apart, Dean became more. Unconsciously preparing for his destiny.
Then John disappeared and Dean went to Stanford.