Mary takes Dean and Sammy stargazing when Sammy is three months old to get the brothers to bond. They lay in the grass in the backyard, Dean snuggled up to his mother and Sammy held carefully but tightly in the four-year-old's arms. Mary points out the brightest ones.
"Dean, look there. See? It's called the Big Dipper."
Dean smiles and snuggles closer. Mary goes on to talk about the monsters and heroes in the sky. Sammy begins to cry.
"Sammy, it's okay. The monsters are all the way up there. They won't get you, I promise. I'll protect you before they hurt you." Sammy clutches Dean's finger and falls asleep. Dean presses a chaste kiss on his baby brother's forehead before drifting off, still clinging to Sammy tightly.
The night after they bury Mary, John is drunk again. 'That's the fourth time this week,' thinks Dean. He picks up Sammy and brings him outside, the stars shining brightly.
"Sammy, look! The Big Dipper, remember?" Sammy laughs for the first time since Mary's death. Dean kisses his forehead again.
"The monsters got mommy, but they won't get you. They'll have to go through me first." Dean's voice is steel, but Sammy is comforted as though he can sense the love in the words. Sammy sleeps in Dean's arms.
When they move the first time, Sammy comes to Dean's room in the middle of the night. The toddler is crying, and Dean leads him outside, sneaking past a passed out John.
The two boys spend hours pointing out the stars and laughing and talking (mostly Dean, as Sammy can't really talk well yet). Sammy falls asleep in Dean's arms, and is carried back to his bed and tucked in. Another kiss on the forehead and a whispered, "No monsters, Sammy, promise," from Dean and then the older boy heads back to his room.
After Sammy kills his first - just a squirrel, but still - he can't sleep again.
Dean brings the young boy out back and tells him stories of the stars. Sammy is enthralled.
When he finally falls asleep, under the blanket of darkness which just shows signs of pale light in the distance, Dean brings him back inside and tells him he's safe from the monsters.
Throughout school, whenever one of them is upset, they go outside and point out the stars. They are often found the next morning asleep in the grass by a hungover John. They don't even care when he yells anymore.
After a particularly bad nightmare, Sam gets up to find Dean, only to remember that the boy is probably thousands of miles away, as Sam ran away to go to college. He goes outside anyway, and points out the stars to himself.
Little does he know Dean is doing the exact same thing.
The night after Jessica dies, they lay together on top of the Impala, neither can sleep.
They point out the stars and they laugh and talk and it's just like old times. Sammy falls asleep first like always.
"I'm sorry, Sammy, I'm so sorry. I said I'd protect you from the monsters, but they got to you anyway."
After John dies, they spend another night outside with the stars.
Neither has their heart in it, though.
When Dean is in Hell, he thinks about the stars.
After Dean comes back, they try to stargaze again, but it's strained and uncomfortable.
They stop.
While Sammy is locked in the cage, his soul thinks of the stars. Dean goes out on good nights and gazes with him. Sam's body doesn't stargaze.
After Dean starts hunting with Sam again, he tries stargazing. Sam won't.
They stargaze again after Sammy gets his soul back. After Cas dies, Dean's heart isn't into it. Sam's hallucinations start to interfere with the peace.
They stop again.
In Purgatory, Dean wishes there were stars to gaze. Sam can't gaze without crying.
They stargaze again once, while doing the trials. It's tense and Sam won't talk much. Neither will Dean.
After the Fall, and everyone being reunited, Sammy and Dean stargaze again. Cas finds them, and joins. Then Kevin does too. Soon everyone at the Batcave is lying on the grass, laughing and talking and crying some too.
Dean squeezes Sammy's hand.
The aren't the only ones each other have anymore.
They have a real family now, messed up and crazy as it is.
The stars shine brightly.