Sam didn't mean to watch his brother sleep. It was just the easiest time to see him, without being caught staring too long or letting his eyes rest on that thick and supple lower lip. He's imagined nibbling that lip so many times, that he can almost taste it.
Dean was dreaming deeply; his eyes darting quickly under the delicate skin of his eyelids. This looked like it might be a nightmare. Sweat was beginning to create a sheen on his brow and along his top lip. Dean's hands were clenched into fight, angry fists.
Usually when this happened, Sam would gently but firmly rub Dean's shoulder. Not enough to wake him all the way, but enough to let him move out of the nightmare - to let him figure out he was dreaming and to change direction. It's happened a lot since Hell. For most of the first year, Dean had multiple night terrors. Sam wasn't sure if Dean even remembers having them. He hoped not. His brother's screams were the soundtrack to what Hell must have been: Absolute fear, unparalleled sadness and exquisite pain.
The dream was getting more intense. When Dean's legs began to fight against the blankets, Sam kneeled next to the bed and reached for his shoulder. Sam's hand rested above Castiel's mark with a warm and reassuring weight. Sam could feel his brother's pulse, the blood sliding rapidly, just under the moist skin. Before Sam could decide whether to grip the shoulder more firmly or to rub light circles, Dean's eyes were open; unfocused and searching for a target.
His bleary eyes found Sam and with both hands, grabbed him roughly. In a matter of a few seconds, Dean had managed to lift Sam from the floor and heave him over his own body to the other side of the bed; rolling over Sam's pinned body to straddle him against the mattress.
Sam was scared. He could probably break this hold, but fighting back could be dangerous. He wondered briefly if he could be killed by his sleeping brother when Dean leaned down and buried his nose into Sam's hair, inhaling deeply. He pushed up, straightening his arms and smiling broadly before coming back down, very slowly this time. Sam stared back, his eyes wide. This was kind of everything he'd ever hoped for. Dean's body, pressed hotly against his pelvis. Even more than waking Dean, Sam's priority was to stop his body from responding to this closeness.
Dean kept Sam's arms held tightly as he rubbed his lips against the lips of his speechless and helpless little brother. "Don't fight, Sammy," he whispered against his ear.
Sam's resolve softened as his body hardened. Hunger and frustration. Dizzy. Lips and tongues, breath. Dancing, slipping and intoxicated. Promises of long-held desires, fulfilled. He felt Dean's growing erection, trapped between them.
"Dean," Sam whispered, because It's The Right Thing To Do, "You're asleep. Wake up."
"No, Sammy. I'm not." He rested his elbows on either side of Sam's head and pressed his body to Sam's panting chest.
Sam whimpered into the dark; grabbing the sheets below him tightly as he lost any will he'd had to resist. His cock surged to fullness as he strained upward against Dean's body, craving more contact. Dean laughed as he kissed him again, before taking a full handful of his hair and pulling his head to the side. Dean's face hovered so close that Sam could feel him brushing against the fine hairs that rose from the goosebumps on the skin of his neck.
"I'm not asleep, but YOU are, Sammy." Dean's fiery eyes softening, beginning to fade. "I'm sorry."
The phone was ringing. Sam rolled over to grab the receiver. "Wake up call."
"Thank you."