It was a night like any other in the Winchester home. Dean stood on the rail of Sammy's crib to say goodnight. John came home from work just in time to help Mary tuck him into bed. Each night like clockwork Mary would kiss him on the forehead and tell him that angels were watching over him. He snuggled under the covers and drifted off to sleep feeling loved and protected.
This night Dean was awoken to the pounding footsteps of his father down the hall past his room. Then out of the darkness, his screams for Mary. Tromping out of his room, he's met with John handing him Sammy, yelling for him to take his crying baby brother outside.
Confused and scared Dean runs down the stairs and out the front door. In the yard he stands on the lawn staring at the only home he's ever known going up in flames. As he waits for his parents to emerge, he glances down to see his baby brother sound asleep in his four year old arms. This was the moment he knew he was meant to keep his brother safe at all costs. He had no idea at the time what that would actually mean.
Sam had gotten out of the life and into Stanford. Dean was torn about being left alone with John. His emotions ran from angry and disappointed to depressed and lonely. He pushed his feelings down and hunted beside his father for two years. He took on all of John's anger and frustrations. No one will ever know the kind of abuse he endured at the hands of his demon obsessed father.
He knew he was meant for the life of a hunter. He wasn't book smart nor did he care about school, but Sam was smart and deserved a life filled with friends, a girl and a 9 to 5 job. Ultimately he was proud of his brother for pursuing a life outside of hunting, even if he never said it to his face.
When John left Dean to follow a lead on the demon that killed their mother, Dean waited in the dingy motel room he and John shared for days. He paced and worried. Called his father, getting no answer.
Hating the very idea of asking Sam for help, he continued to search on his own to no avail. Along the way he must have dialed Sam's number a thousand times only to hang up before it connected. How, after all this time, could he disturb the life Sam had made for himself at school? But Dean was scared. The little boy inside of him wanted, no needed someone to tell him things would be alright and the only person who could help calm his nerves was his brother. He packed the Impala and drove to Stanford. He needed his little brother and would say or do anything to convince him to come with him to find their father.
He barges into the apartment where Sam lives with Jessica to Dean's surprise. He's hit with the green eyed monster of jealousy. Sam really was living a normal life. One he knew he could never have.
With the promise of an easy job to complete for John and maybe a clue as to his whereabouts was all Sam needed to get on board.
After the woman in white Sam reminded Dean he had to return for his law school interview. He drops him off in front of the apartment building.
To be honest Dean was jealous of the life Sam was building. Sitting in the Impala he tries to think of some excuse to get Sam back. The thought of continuing to search for their dad alone terrified him. Out of the corner of his eye he noticed what could be burning red flames and realized it was and it was coming from Sam's apartment. He ran inside to find Sam yelling at Jessica burning on the ceiling. With speed he pulls Sam out of the apartment and down to the Impala.
The sheer horror in Sam's eyes brings tears to Dean's eyes. Again he was reminded that he has to keep Sammy safe at all costs.