Sam was twelve when he found out his brother was allergic to cats. It had never really come up before... and when Sam had brought home a stray he'd found rooting around the motel trash bins, Dean had started sneezing.
"Sammy get that thing out of here!" Dean said, sniffling, "I'm allergic."
Sam instead clutched the cat, looking down into his eyes, "But... he's all alone. I can't just leave him out there, Dean."
Dean rubbed his now red eyes, and then sighed resignedly. He looked at Sam, who was giving him the puppy-dog eyes, and then at the cat, who inexplicably had the same expression.
Dean threw his hands up in the air, "Fine! Keep it for now, okay? But if dad gets angry, don't go blaming me. You can take him to a shelter in the morning."
Sam grinned and snuggled the cat against his face, "Thank you Dean!"
Dean smiled at his brother, but responded snidely, "Yeah, yeah, whatever."
That night, he couldn't help but grin when he saw his brother fawning over the cat. He played with it long into the night, and fell asleep on the couch with it on his lap. When morning came, Dean was almost sad to see the little critter go when they took him to the shelter. Seeing Sam smile like that was worth so much.
Dean ruffled Sam's hair when they left the shelter, "Don't worry Sammy. He's going to a good home."
Sam sighed, "Yeah... you know, when I get older, I'm gonna have a pet. One I can bring with me everywhere. A cat, or a dog."
"Maybe one of those naked mole rats so I don't sneeze all the time, huh Sam?" Dean grinned.
Sam pushed Dean's hand away from his hair and grinned back, "Well, whatever happens, at least we'll be together, right Dean?"
"You got it Sammy." He thought for a moment, "I'm not your pet though."
Sam grinned and took off running, "Here boy! Come on Deany! Want a treat? There's pie at the motel!"
Dean looked at his brother incredulously, and then walked after him, smiling ever so softly. Yeah. They'd always be together.