Dean hated what happened to Sammy. He let it happen, after Dad told him to watch over his little brother.
Worst of all, HE is the one that did it. Hurt him. So, to make sure it would never happen again, he decided then and there that he would make sure that his little brother was taken care of, even if it meant no more games.
This particular time, they were in a run-down motel room in a Podunk town, in the middle of nowhere Nebraska. In winter. Snow…well it was bad enough that Dean was running low on food for Sammy (because as long as Sammy was okay, Dean was okay).
"Do you wanna build a snowman? Come on let’s go and play! I never see you anymore, come over here, it’s like you’ve gone away!" Sam begged.
Dean turned over, folding the pillow under his head, trying to ignore the hunger pains.
"We used to be best buddies, and now we’re not, I wish you would tell me why!" Sam pleaded. "Do you wanna build a snowman? It doesn’t have to be a snowman."
"Go away, Sammy!" Dean said.
Sam looked down, tears forming in his eyes. “Okay, bye.”
Nothing really got better from there. Years passed, and Dean still did his absolute best to take care of his little brother, even if it meant getting suspended from school.
"Do you wanna build a snowman, or ride our bike around the room? I think some company is overdue, I’ve started talking to the pictures on the walls!" Sam said. Dean rolled his eyes…Sammy was always melodramatic. They’d only been here for a few days, and Dean wasn’t allowed to leave, not after beating that stupid kid up for calling Sam names.
"It gets a little lonely, all these empty rooms, just watching the hours tick by…" Sam then proceeded to make ticking noises with his mouth.
"Stop!" Dean said, his head in his hands. Books lay scattered on the table in front of him, homework he’d have to complete while he was suspended.
"What did I do, Dean? You never hang out with me anymore, and the only time you hang out with me is when you’re punished!" Sam retorted.
"Just stop, Sammy."
"Stop calling me Sammy!" Sam replied. "I’m almost 10."
John came in the room at that moment, and the two shut up. Sam returned to doing his homework, because no matter what they did, Sam knew he had to get good grades. It was important.
Many years passed, Sam and Dean both grew up. Dean soon became old enough to drop out of school and become a hunter, just like his dad. Sam stayed in school, wanting to at least have that going for him. He squirreled away college applications, and filled them out while Dean was doing something to help their dad.
Then, one day, he got a letter telling him he’d been accepted to Stanford. It was happening; he was going to college, on a scholarship. He wanted to relish in his success and he told Dean, but all Dean did was get upset and lock himself away, in the room. Sam was stuck outside, where there was snow gently falling.
"Dean? Please, I know you’re in there. Dad is asking where you’ve been. You said have courage, and I’m trying to, but I need you too, just let me in. We only have each other, it’s just you and me, what am I gonna do? Do you wanna build a snowman?" Sam begged, his head lying against the door separating the two.
Dean rested his head against the door, trying to fight back tears (because he was a Winchester, and Winchesters didn’t cry). How could Sam do this? Run off to college?
It was past the time to build snowmen. Sammy was growing up, and running away. Dean’s job was done.