Momma
At four years, ten months, and nine days Dean became Sam's family. Maybe this wasn't quite fair. After all, John was the dad, and he was there at least some of the time.
But not all the time. He wasn't there when Sam was seven, and lost both his front teeth after he fell off the monkey bars. John also wasn't the one who snuck two quarters under the motel pillow and took Sam to the nearby convenience store the next day either.
John wasn't there when Sam was ten and broke his arm after trying to teach himself to ride a bike. Dean had whacked him upside the head and spent the next week teaching him to ride one handed.
John wasn't there when Sam needed a new pair of shoes, his socks poking out of his second hand sneakers. It had been Dean who dug in the glovebox, the bottom of the duffle bags, and finally charmed the Goodwill cashier into giving him a fifty percent off on the one pair of size thirteen reeboks.
John wasn't there when Sam curled in on himself, hungry, sick and exhausted after a bout of flu. Dean had falsified his first credit card account after that.
John wasn't there when Sam took his first steps towards Dean and the bottle the five year old was holding.
John wasn't there for many things. And Dean cherished this. In a life he couldn't control, when you didn't know where your next meal was coming from, or where your favorite pair of socks went (that particular pair was eventually found in the cushions of the Impala when Sam was looking for a pencil. Dean had been heartbroken to find that they were now too small, and they were repurposed to clean guns), having a two year old look up at you with big, watery eyes and asking you to 'kiss his boo-boo' was exactly what kept you from going nuts.
So Sam grew up, all Dean's baby. At one point, John had tried to step in, when Sam was three and Dean was seven. Dean was sick with the flu, a little curled up ball on his lumpy motel bed, when Sam smashed his finger between the bathroom door and the wall. First hiccups (which John ignored, hopefully thinking that maybe if he ignored it, the toddler would man up) and then, when Dean didn't come to his aid, sobs broke out.
John was many things, but he wasn't stonehearted. His older boy needed sleep, and Sam needed comforting. The dusty old book could wait ten minutes for him to comfort his youngest and get his oldest a glass of water. So he got up, and crouched down next to the wailing bundle, carefully picking him up and murmuring quietly.
Sam pushed him away, crying louder. John stared as the baby curled back up on the floor, huddling in on himself and crying louder.
A raspy voice called John out of his stupor. "'Ive him to me." Dean pushed himself into a sitting position, wincing. Sweat clung to his forehead and he was shivering, but he was holding his arms out, waiting for his baby brother. John glanced down at Sam as the wails got louder, and deciding that he wasn't going to get any quieter, picked the struggling toddler up and gruffly deposited him on Dean's bed. To his surprise, Sam immediately snuggled up to Dean, his wails subsiding as Dean began to pet his hair and tiredly examined the abused finger.
It was that night that John realized two things: 1) Sam did not want or need him, and 2) that he had failed. That night he spent the room money on a bottle of whiskey. Four days later, fully healed, Dean looked at him reproachfully as he tucked Sam in in the back seat of the Impala. John realized that night that he had failed both of his sons, and what was left of the bottle disappeared in an alleyway.
Sam didn't seem to realize at first that Dean went above and beyond the duties of a big brother. It wasn't until he hit sixth grade and unpacked a peanut butter and banana sandwich that he would realize. And even then, it wasn't until Dan from english sighed, looking down at his carrot sticks, and said, "I wish my mom would pack me something like that."
"My mom isn't around." Sam blinked, surprised, unwrapping his sandwich and poking around in his brown paper bag, hoping for a fruit roll-up (it did happen occasionally, when Dean found an extra dollar or two, or John was trying to apologize for something).
"Your dad made that?" Dan's voice was slightly awed. His father had nothing to do with the food in the house unless he was paying for it or eating it. Dan's mother often remarked that her husband could (and indeed, had) burn a salad.
"No, Dean did." Sam was almost squinting at Dan now. Whose older brother didn't pack their lunch when they were doing research until late the night before for a hunt?
"Wow."
And Sam began to grasp that Dean was playing more than the big brother role. He forgot this only three days later when he found all his socks knotted together in a long chain. When he complained to John, his father had simply shrugged, a grin playing about his face and said, "Boys will be boys." John regretted this when Sam retaliated on Dean, leading to sporadic prank wars. Dean was more brutal, but Sam was sneakier. When Sam was sixteen, the prank wars escalated to the famous nair shampoo, which caused Sam to sulk for days and John to put a permanent ban on pranking.
The next time Sam began to guess Dean's above and beyond care was when he was twelve, and he slit himself in a knife training accident. Dean had stitched up his arm, grumbling half the time about idiot little brothers, and the rest of the time mumbling apologies as Sam winced. That particular episode had resulted in ice cream and a lecture from John, who was beginning to wonder if Sam would have ever made it without Dean.
At fifteen, Sam was making coffee in the motel while Dean cleaned the hunting equipment. It was the first hunt the boys had gone on without their father, and it had come out alright, neither boy injured beyond bruises. Sam didn't know it, but Dean had been worried sick about the simple salt-n-burn, convinced that this was the time Sam would get hurt. But he hadn't, and was now wrinkling his nose at the cheap coffee as he poured two mugs, handing Dean his customary black, and dosing his liberally with milk.
When Sam hit seventeen, and suddenly sprouted, growing from an armrest to an invitation to a neck brace seemingly overnight, Dean had bought him an entire new wardrobe, even springing for a brand new (And oversized, just in case) canvas coat that Sam wore everywhere until a wendigo shredded it. Dean also stood in the background, giggling like a mad man when Sam tried to fend off the hooker who was entranced with his shaggy hair and dimples, exclaiming loudly over his 'pretty eyes'. She seemed to think he was older than he really was, which resulted in Sam contemplating whether or not he could build a time reverser and avoid the weird conversation altogether by insisting that he and Dean eat popcorn in front of a bad quality TV instead of going out for burgers.
Years later, when Sam was twenty-five, he finally sewed all the pieces together, and looked over at his brother. They were in the Impala, Dean with only six months left until the Hellhounds would drag him away.
"Thanks." He said quietly, toying with his phone.
"What for?" Dean blinked at him. Sam had been sappy lately, what with the deadline and all, but this had never happened before.
"For being there." Sam shrugged.
And Dean knew what it was about. It was about the hundred little things he had done for Sam over the years, the things he didn't pause to think about, that Sam had taken for granted, not the one big thing that they were now facing.
It was about the things Dean had done because someone had to. The mom and dad and brother and best friend duties that he had never, ever shied away from.
And Dean choked up, realizing what he was leaving behind.