Dean didn't wake Cas up before he left the next morning. He wanted the Omega- who was feeling warmer than the day before- to get as much sleep as possible. He swore to himself that he'd come home for lunch, just to check up on Cas. He left quickly and quietly, Cas still sleeping soundly in the bed. When Sam arrived a number of hours later, he first looked on the couch for the sick Omega- he wasn't there. With a shrug, Sam made his way back to the bedroom. He quietly opened the bedroom door and peeked in. He instantly slammed the door shut, backing away quickly, his face flushed a deep red.
"He's not sick, you idiot." Sam didn't know if he was talking to Dean or himself. "He's in heat." Sam breathed heavily through his mouth, but now that he had smelled the beautiful Omega's scent he couldn't get it out if his head. "Go, now, Sam. Get out of here before you do something you'll regret." Despite his words, Sam found himself creeping towards the bedroom again, breathing deeply to try and catch more of the tantalizing smell. He hesitated only a moment outside the door. Then he pulled it open quickly, took a small step inside, and slammed the door shut behind him. Cas's heat-smell filled the room and Sam's cock hardened quickly.
"Alpha, please." Cas's eyes were closed, and he was writhing naked on the bed. Clearly he thought Dean had entered the room. "Please, Alpha." Sam groaned and gripped himself through his jeans. Cas's eyes popped open at the unfamiliar sound. "S-Sam!" he cried, attempting to cover himself, eyes wide with fright. Sam's tail swished aggravatedly behind him.
"Hello." he greeted, eyes trailing over the Omega before him. "Dean asked me to come over, see if you needed anything while he was at work." Cas but his lip and shakily covered himself with a blanket.
"Please, sir. Please call Dean. Tell him..."
"No," Sam took a step towards the bed. "We wouldn't want to bother Dean while he's at work. But don't worry, I'll take care of you." Cas shook his head frantically as Sam continued his path towards the bed. Cas stood, putting what he could of the bed between them.
"Sam, please, please go call Dean." Sam just shook his head, eyeing the small boy's erect dick.
"I've never had an Omega during it's heat." he murmured. Cas tried to run past him, tried to flee the room- but Sam grabbed him around the waist, tossed him back onto the bed. He followed immediately, covering the small body with his own.
"Sam, no, please don't." Sam's fingers unerringly found the Omega's hole, circling the clenching muscle.
"Come on, Castiel. You know you've love to have me deep inside you, love to have my knot stretching you wide open. You know you'd love to be my Omega." Cas struggled as best he could with Sam's weight pushing him into the mattress.
"He's your Alpha too, please don't do this." Sam's instincts were screaming at him to claim, to breed, to make the Omega his. He pushed gently on the center of the ring of muscle, surprised at the give.
"You want it, Cas. You want me." Silent tears streamed down Cas's face as Sam's finger breached him. Sam just let out a low groan and immediately added a second finger, exploring the hot cavern with his thick, hot fingers. Cas's inner Omega forced him into compliance, even as he continually whispered for Sam to stop. Sam chose to ignore him, rutting against the boy's stomach as he added a third finger, far too quickly. Cas let out a whine. "Gotta have you now, Cas. I've gonna have you." Sam pulled enough of his weight off the Omega to flip him onto his stomach. Cas tried weakly to crawl away, but Sam stopped him with a hand in the small of his back, holding him in place.
"Please, don't. No, Sam, please..." Sam fumbled with his jeans.
"Gonna be mine."
Dean drove quickly home from work during his lunch hour- he had hoped Sam would call him with an update when he left Cas, but he hadn't. Dean wasn't worried of course, but he was worried. He opened his front door- and was immediately hit by the smell of an Omega in heat.
"Cas," he all but moaned. He hurried for the bedroom, and just outside the door, he smelled something else. An Alpha. The scent was too strong for the Alpha- Sam, he recognized- to be gone. Horrified at what he might find, Dean threw open the door. It slammed into the wall with a loud bang. Dean heard Cas whimper, heard his pleading, but his gaze was focused on his brother, who only spared him a glance before returning to his work- Dean barely registered that Sam was still in his pants before he pounced, yanking his brother off the shaking Omega. "Get out while I'll still let you, Sam." he growled, positioning himself between the two men. Sam stood and growled back.
"He's mine, Dean." Dean's face grew stormy and his tail swished behind him.
"Mine." Sam sneered, looking directly into Dean's eyes. Neither man looked away, Sam too hyped up on hormones to realize how angry he was making his brother. Never breaking eye contact, Dean pulled his fist back and slammed it into his baby brother's cheek, knocking the other Alpha to the ground. He followed him down, punching his face repeatedly until he heard Cas moan, still on the bed. The testosterone increase in the room was affecting him.
"Alpha, Alpha, please, please, please, I need you, please." Dean felt himself begin to harden and he stood from his brother. He dragged Sam from the room, from the apartment. He took Sam's key to his apartment off his key ring, and deposited him outside the front door, before returning to his Omega.