Twenty-Three.
When he was six, Sam told Dean that he was going to marry a beautiful girl with long yellow hair when he was twenty-three.
"Don't be stupid," Dean scoffed. "You can't know that. Besides, what do you want with girls, anyway? They're stupid." Dean, at age ten, was very certain of this one important fact, and had just recently had it reinforced when Marcie, the prettiest girl in the class, had made fun of his ripped clothes. What did she know, anyway?
"Everyone gets married someday," Sam said. He knew this from the TV, which was one of their more constant companions. "Dad got married."
Dean got real quiet after that, and for a little while, the topic was forgotten.
A week later, though, he said it again. "When I'm twenty-three," he said, "I'm gonna get married to a pretty girl with long yellow hair."
"No you're not," Dean said. He was tired of this topic already, and was in the middle of cleaning their knives anyway, and if he didn't concentrate, he knew he'd get cut and Dad would yell at him.
"How do you know?" Sam demanded.
"Because you can't know who you're gonna marry, stupid," Dean informed him. "You meet them and fall in love and live happily ever after. That's what Dad says, anyway."
Dean knew his Dad was lying, though. Mom died, and if mom could die, then there was no such thing as happily-ever-after, not for anyone. Not if you could love someone and they could die.
Sam didn't understand that, though. He was only six, and anyway he hadn't known mom. No one he'd loved had ever died.
"I just know, okay?" Sam said. "She's gonna be smart, and funny. Her eyes will be green. She's gonna kiss me on the forehead like Dad does when he puts me to bed, and her favorite color will be blue. We're gonna get married and live happily ever after. But I know it'll be her."
"Whatever," Dean said. He didn't want to talk about it any more. He knew that it would never happen.
The day Sam left for college, Dean couldn't help but wonder if he'd find his pretty girl with the long yellow hair. He wondered if she'd be smart, and funny, and if her eyes would be green and if she'd kiss Sam on the forehead like Dad used to do. He wondered if hef favorite color would be blue.
He liked to think that he hoped Sam wouldn't find her, but he knew he was lying. If anyone deserved his dream girl, it was Sammy.
And at least one of them had a chance to fulfill his dreams. Dean complained the same as Dad about Sam running off, but secretly, in the dark of the night, he wished his brother all the best.
Because Sam deserved it.
Standing in Sam's ill-lit living room, Dean stared at Sam's girlfriend. She was very pretty, with long blonde hair. She must be smart, if Sam had picked her. She might even be funny, and looked like the type to kiss you goodnight on the forehead.
Even in the low light, her eyes were green. And she wore a blue t-shirt with Smurfs on it.
And Dean knew that he'd lost his brother forever.
Sam was only twenty-two when his pretty girl with the long yellow hair died in blood and flames on the ceiling above him. Dean came back for him and saved his life as he screamed her name, over and over, but it wouldn't bring her back. Nothing could ever bring her back, and she was gone forever.
Sam finally understood what it meant to lose someone that you loved.
Jessica had been Sam's very first precognition of the future. She was the only one that had ever been wrong. That ever would be wrong.
Somehow, he knew this. And when he dreamed that his father would be killed with his own gun by a terrified bystander, he woke up with a gasp and then checked to make sure that Dean was still asleep before allowing himself to grieve.
On Christmas Day, they stood in the morgue and identified their father's body. John Winchester looked older in death, somehow. Like the intelligence and burning passion for vengeance that had driven him and lit his face were gone, and without it he looked his years.
Dean couldn't look at him, lying there like that. He turned away, aware that he was crying, and not caring, even though he hadn't cried in years.
Sam stood there for a long time, and didn't grieve. He'd been already shed his tears for his father's death, long before it had happened.
Eventually, he turned away from the shell that had once held John Winchester, and said, his voice very quiet, "Where to next?"
Sam was twenty-three when he died. He was killed by the thing that had killed his mother, who was Dean's first loss, and Jess, who was Sam's. Sam's last act on this Earth was to say the words that would bind it into corporeal form, and as Sam lay bleeding on the oil-slick pavement, Dean sliced its head off with his brother's knife.
"Sam," Dean whispered, his hands on Sam's body gentle despite the frantic worry in his voice. "Oh god, Sammy," he said when he encountered the gash on Sam's stomach. Sam was going to die the same way his mother and Jess had died. It seemed strangely fitting.
"Dean," he said, forcing the words past the pain. "Dean, can you do me a favor?"
"Anything," Dean said.
"When I die, burn my body."
"Don't you think we've had enough flames, Sammy?" Dean said.
"Full circle," Sam explained. "And don't call me Sammy."
"I'll call you whatever I want to call you, little bro," Dean said. "I love you, you know? What am I supposed to do without you?"
"Get a real life," Sam told him. "It should be a learning experience for you." And then the edges of his vision went gray, and he offered Dean a beautiful, terrible smile that would haunt Dean for the rest of his life. "Dean, do you think that they have weddings in Heaven?"
"Absolutely, little brother," Dean said. "I wish I could be your best man."
"You will be," Sam said. "I'll be twenty-three forever, you know. I can wait."
And then he was gone.
Dean was forty-six when he died. He'd never married, had never had children. And he'd never stopped hunting.
But he had fallen in love. She was a tiny slip of a thing, with long dark hair and huge dark eyes. She could break Dean in half with her little finger, but instead she always just tickled him and turned her gun on the monster under the bed. He'd adored her, and he'd mourned her when she was killed by a werewolf, two years before.
But he wasn't too sad. He knew that his time was coming. And he knew that when it did, there would be a double wedding in Heaven.
Because Sam was still twenty-three, and he would finally marry his pretty girl with the long yellow hair.