A/N: Once again, my amazing beta Sarah_Ellie has saved me from myself.
"Hey, you should get some rest."
Dean's eyes flicked from the road to the rear view mirror. A weird sort of twist happened in his chest, watching Joe pull his brother in against his side, encouraging the younger boy to go to sleep.
He looked across the seat to Sam for a moment, who returned the glance with a wistful look in his eyes. Dean's eyes flicked back at the boys before turning back to the road with a nostalgic little smile at the corner of his mouth. It was another 15 minutes until they reached Merritt, and the asphalt was empty before them.
Dean turned the radio on low as yellow stripes on the road slid past.
"...got nine lives, cat's eyes, using every one of them and runnin' wild. 'Cause I'm back, yes I'm back, well I'm back, yes I'm back..."
It could have been a scene from their own childhood, the rumble of the Impala engine cutting through the quiet night, and two small boys in the back seat trying to help each other sleep.
"...Well I'm back back! Well I'm back in black! Yes I'm back in black! Back in the back of a Cadillac..."
Sam had never really been a great sleeper. He slept lightly, for one, and he was too restless, for another. The kid's brain moved a million miles a minute, and it seemed to Dean that he could never really turn it off long enough to get some proper shut eye. The fact that the poor kid was sick at the moment didn't help either.
Dean winced in sympathy as Sam coughed raggedly again, curled pathetically against the door with his legs drawn up to his chest. He tried to pull the extra layers of clothing draped over his small frame tighter around himself, fighting the chills that sent his body trembling.
There was a bottle of cough syrup in the back window, half empty. He'd probably ask his dad to buy some more when they stopped next, whenever the hell that was going to be. Dean could admit he was more than a little bit ticked at his father at the moment; mainly for flat-out refusing to halt their travels while Sam was feeling so ill.
So instead, poor Sammy had to tolerate the loud rumble of the car's engine and the cramped back seat while he was practically coughing up his lungs instead of lying in a quiet bed like he deserved.
Dean reached for the medicine bottle as Sam coughed again, giving a small, miserable groan when he caught his breath, rubbing his sore throat.
"Here, Sammy," Dean said gently, pouring a heavy dose into the medicine cup that fit over the lid of the bottle and handing it over.
Sam took it with a hoarse thanks, making a face at the unpleasant taste.
"You should try to sleep," Dean encouraged, and Sam snorted.
"I can barely breathe, I don't think sleep's gonna happen," Sam mumbled miserably, and Dean sighed, glancing irritatedly at the back of their father's head in the driver's seat.
"You should try anyway. Come 'ere," Dean insisted, reaching across the seat to tug on Sam's arm, and Sam shuffled over with a sigh, letting Dean tuck him against his side.
Dean pushed Sam's bangs back from his forehead to check his temperature, and Sam took it as an opportunity to lay his head on Dean's shoulder and settle in as best he could in the small back seat. He was a little warm, but not feverish (yet), and Dean frowned with concern before flattening Sam's bangs gently down again.
"Am I going to live, Dr. Dean?" Sam smirked, and Dean snorted, tugging on a lock of Sam's hair.
"Nope. Incurable. You're just going to have to suffer an awful, coughing death."
Sam gave a small laugh that tuned into a cough, and he turned his head away from his brother to muffle it in his sleeve.
Dean rubbed his shoulder gently, apologizing.
"S'ok," Sam gasped when the coughs had subsided, laying a hand over his chest and wincing, "I'd be coughing either way."
"The medicine will kick in soon," Dean offered hopefully, letting Sam lay his head back against him again.
"Yeah," Sam mumbled, closing his eyes.
Time passed in silence after that, Sam's coughs slowly easing with the aid of the cough syrup, and they finally quieted enough that he was able to fall asleep, breathing slow and heavy against Dean's neck.
Dean risked checking his temperature again, and left his hand resting gently on Sam's forehead affectionately.
"...back in black! Yes I'm back in black!"