Sam and Dean never stopped anymore. They never paused; they were always too tired to sit and watch TV in the motel- too busy to sit on the Impala and watch the stars anymore. So, it ended up being Dean alone most of the time. While Sammy was sleeping, he could slip out of the motel, drink a beer on the hood of the car, and look up at the stars. It didn't feel the same; it hit his heart like a truck, aching and breaking. Every time he thought of Sam, what they now meant to each other, what went wrong. He still loved his baby brother; more than anything, but it was hard. They were different; there was nothing else to be said about it.
Occasionally friends would join him there. Bobby would sometimes have a beer with him late at night, when Sammy was off doing research. Bobby would complain about getting old while Dean would smile and look down at his beer, listening. Bobby was good to listen to; he was a comfort. He would tell Dean stories of hunts: close calls, mysteries still unsolved, or whatever came to his mind.
They would end the night shaking hands, Bobby driving off in his car and Dean sitting on his own again. Dean would raise his glass while Bobby pulled away, both of them smiling, and one wave. But now, Bobby wouldn't sit with him. He was gone.
A couple times, years ago, it would be Jo. Dean would try to empress her, singing her classic rock songs, and she would laugh and sing along. They would talk about Ellen, trying out their impressions of her. Jo would laugh as Dean pursed his lips, and put his hands on his hips. Jo's laugh would make Dean smirk, and he would take a sip of his beer, and lie out on the Impala, looking up with a stupid smile on his face. Jo would slap him on the knee, say something like, "Goodnight, Idiot." Ellen would call if it got too late, and she would pick Jo up, scowling at Dean, thinking to herself that she wished Dean could be her son-in-law. Then they would drive away, and Dean would have the smile on his face whenever he remembered something funny he said that made Jo laugh. But, they didn't come anymore either. They were gone, too.
One night it was Bela, after one of the hunts they worked together. Dean had left, and she found him sitting on the car. She didn't feel like fleeing from the Winchesters quite yet. He didn't know why she walked up to him with a cold smile, and sat with him. He guessed she was lonely; tired of disguises and chases for a time. So they sat there, and they flirted a little. Bela was distracting Dean from the stars; he was caught looking at her face and her body when she wasn't looking. And she did the same thing to him. That one night was a time when enemies set aside their differences to look at the stars together, to look at each other. But, that never happened again. Too soon after, Bela had been dragged away as well.
Ben joined him often, for that brief year. Of course: not on the Impala. That was to be hidden, kept away under a tarp. But, they would sit out together. Dean would pretend to know the stars above, and Ben would correct him. They laughed together, and once, Dean can still hear it very clearly in his head, Ben called him "dad." He could tell it was on accident; Ben knew Dean wasn't his father, but as Ben laid down next to Dean on the hood of Lisa's car, he felt right to whisper, "this is great, Dad." Dean would have traded the rest of his life in a heartbeat to have that moment back.
But, the best of nights, those were with Cas. Those were always the darkest nights: the ones with the occasional tear, the ones where he thought for a moment about driving away. Those were the nights that Cas came. He would sit on the car with Dean, and he would be quiet. They wouldn't chat about this and that; they wouldn't try to start or keep a conversation going. Instead the just watched the stars. Occasionally Cas would point out constellations; saying that he and his brothers designed them. Dean asked him once which one he had made. Castiel pointed to Sagittarius: the hunter. This made Dean smile.
One night Dean was sitting alone, looking upwards, and thinking of his Dad, as he often did. He heard a door behind him, not expecting any one tonight. Cas was off, god knows what was happening, and the long list of other friends had been cut short. But Sam Winchester smiled at Dean, and slid next to him without a word. Dean couldn't help the smile that crept up his face. The two brothers sat there together, silently, the way they used to. They were content for the first time in a very, very long time. That night, they were just two traveling brothers, living their life the only way they knew how. Dean opened a bottle of beer for his brother; Sam raised a glass to Dean. The Winchester boys were happy.