When Castiel suddenly appears in Sam and Dean's rundown motel room, Sam looks up from his laptop with a smile. "Hey Cas."

"Sam," Castiel says with a nod. Anyone else might take offense to Castiel's curt reply, but Sam knows better. He's learned to read Castiel after all this time, and there's a faint hint of affection in his voice and warmth in his eyes that belies his words. Then Castiel turns to Dean, and all that warmth intensifies into something that burns stronger than friendship. "Hello, Dean."

Dean sets aside the gun he was cleaning and turns away from the TV, smile on his lips, when he suddenly frowns. "What the hell is that?"

At his words, Sam realizes there's a lump in Castiel's long overcoat, his arms cradling whatever it is against his chest. For one wild moment, he thinks it might be a cat, or some other creature that was abandoned and needed sheltering from the rain. And -when Castiel slowly peels away his trenchcoat to reveal what he's holding- he's sort of right.

Only instead of a baby animal, it's a human child. An infant, really, barely a few months old if Sam is any judge on its age, with tiny hands and feet and the curliest hair he's ever seen. It sleeps peacefully, blissfully unaware as Sam and Dean crowds closer and peers at it. "Cas..." Dean pauses for a moment as he struggles to form words. "Why are you holding a baby?"

Castiel frowns and sounds almost defensive when he says, "He is my offspring, of course."

"But," Dean looks like he can't figure out whether crying or laughing is the appropriate response for this sort of situation.

Fortunately, Sam intervenes before he can decide on which one. "I didn't know angels could have children," he says carefully, not wanting to offend Castiel but genuinely curious.

Castiel -for lack of a better word- blushes. "It is not a common occurrence," he admits. "But my son has proven that it is not entirely impossible." He doesn't quite smile, but it's a near thing as he gazes down at the baby in his arms with the love only a parent can feel.

Dean claps him on the back, hard enough to make any other man stumble. Castiel, on the other hand, hardly moves and only looks back at him in bemusement. Dean grins. "I'm proud of you, Cas. So who's the lucky lady?"

Castiel's brow furrows, but whatever he is about to say is forgotten when the baby opens his eyes. His eyes are dark blue, like Castiel's, which makes his olive skin and black curls even more striking. Sam wonders where he got such features, since Castiel's hair isn't nearly as curly and his complexion is pale. He means to ask, but then the baby looks straight at Dean and smiles a ridiculously big smile. He immediately holds his arms out as if to be picked up, but Dean backs away, eyes wide.

"Um." Dean stares helplessly at the baby before shooting Sam and Castiel a panicked look. "What does he want?"

"He wishes to be carried, Dean," Castiel replies patiently but still sounds as if Dean is the most idiotic person he's ever known.

There's a terrifying moment when Castiel passes the baby to Dean and teaches him how to support his head and tiny body. Dean cradles the baby gingerly against his chest, man and baby staring at each other for a long moment. Abruptly, the baby laughs and reaches out to touch Dean's face.

Sam releases a breath he hadn't realized he was holding. Dean turns to frown at him, looking betrayed. Uh oh. He needs a distraction. Quick. "What's his name, Cas?"

Castiel's expression brightens and he opens his mouth, making sounds a human is normally incapable of producing. Sam and Dean share a look as the baby looks over at Castiel and gurgles a reply. "It's a fine Enochian name," Castiel says, looking crestfallen by their reaction.

"It's a great name," Dean quickly agrees. "But how about we give him a name that's easier to pronounce in English?" He pauses to think a moment. "What about... Blane?"

Sam grins, remembering the movie Dean had been watching just a short while before Castiel appeared with the baby. "From 'Pretty in Pink'? I should have known you liked the movie when you insisted it was the only thing on..."

"Shut up," Dean grumbles, embarrassed. But Castiel seems to consider the name. He leans over the baby and in Dean's personal space, holding out his hand. The baby latches on to his fingers, babbling in a language Sam could only assume was his own. But Castiel listens and nods as if he understands.

"Blaine approves of his new name," Castiel announces when the baby finishes speaking.

Dean looks suddenly sheepish. "It's really just a suggestion, Cas. If you don't like it, you can choose something else. You are the kid's dad after all." Castiel stares at him as if he'd grown an extra head. "Cas?"

"You are Blaine's father as well, Dean."

Dean's jaw drops. "I'm what?"

In retrospect, can anyone really blame Sam under the circumstances? He just can't help himself. He laughs. For a long time.

A very, very long time.

Dean watches Sam steady little Blaine on his knees as the baby bounces around on short legs, making blissfully happy noises. He whirls on Castiel, who stares back at him with an unreadable expression. That just makes him more pissed off, and he finds himself yelling while Castiel's voice is low with barely suppressed anger.

"What the hell, Cas?" he demands.

Castiel's brows furrow. "Dean, do not use such vulgar language in front of our child-..."

"Exactly! When were you going to tell me we had a kid together?"

"I did not have the opportunity before. That's why now-..."

"He doesn't even look a thing like either of us!" Honestly, curly hair? "I bet he's not even mine!"

The moment those words leave his lips, Castiel's expression darkens. There's a loud rumble overhead, like thunder rolling, despite the sky outside the motel window being blue and clear. Dean feels his heart speed up with fear, but thankfully Sam intervenes before things get out of hand. "Hey, hey," he starts and pauses, apparently not sure how to continue. But thankfully Castiel turns away from Dean to look at him just as Blaine whimpers and squirms.

The rumbling immediately stops and Castiel moves forward to pluck Blaine from Sam's grasp. Without even looking at Dean, he sits down at the edge of the bed and pulls a baby bottle out of his pocket. Dean is pretty sure it wasn't there before, but decides not to question it as Castiel cradles Blaine close and feeds him. Blaine greedily grabs at the bottle with his tiny hands and swallows the milk it provides in big gulps.

Dean slowly sits down on the other bed, watching them and trying to ignore the constricting feeling in his chest.

"Blaine is your son, Dean," Castiel says quietly. So quietly he almost has to strain his ears to catch it.

Dean runs his fingers through his hair and sighs. Slowly, he looks up at Castiel, staring into his deep blue eyes. "Start from the beginning, Cas."

Unfortunately, Castiel doesn't get the chance to explain where Blaine came from.

As soon as he finishes his milk, Castiel holds Blaine against his chest and pats his back until he burps loudly. Almost immediately, his face scrunches up and Castiel announces that they need to pick up supplies for Blaine. Which is how Dean finds himself pushing a shopping cart, Blaine strapped in the baby carrier, Castiel grabbing baby formula and diapers and other things off the shelves Dean is trying not to think about. Sam trails after them, suppressing a smile and being entirely unhelpful.

"I don't get it," Dean mutters, watching Castiel dump boxes and packages into the cart. "You have the kid's bottle, but not all the other stuff?"

Castiel stares at him for a long, unnerving moment and Dean tells himself it's not relief he's feeling when he finally looks away. "I didn't have time to bring much with us."

"Why?" Sam asks. He leans over Dean's shoulder and makes faces at Blaine, who laughs even despite the state of his soiled bottom.

Castiel's expression hardens. "Zachariah," he says.

It's all he has to say, really.

"I hate that asshole," Dean growls. He looks down at Blaine and his small, round face, feeling a wave of protectiveness. The baby beams at him and he realizes just how screwed he is, whether Blaine really is his child or not.

When he looks up, Castiel is gazing at them with a fondness that scares Dean more than he's willing to admit.

"Let's hurry up and buy this junk before the kid starts crying," he says quickly and pushes the cart toward the check out line.

The fact of the matter is, there's only one place safe enough to take Blaine. Or at least that's what Dean tells himself, anyway.

If he's being perfectly honest, the main reason they go to Bobby's is to see the look of surprise and slight horror that appears on his face when he opens the front door to find Cas holding a baby. He looks even more confused when he glances at Sam and Dean, their arms filled with bags of supplies for said baby.

"I had no idea I was suddenly a grandfather," he said slowly.

Dean rolls his eyes and shoves his way inside. "You're hilarious, Bobby. Really."

"Hey, Bobby," Sam greets cheerfully. "Sorry for dropping in on you like this."

Dean hears Bobby ask if Sam brought a baby of his own too, frowning when his brother tries to muffle the laugh that escapes and fails miserably. Dean feels betrayed and scowls at Cas like it's his fault, who steps through the doorway and glances at him with a curious expression. In his arms, Blaine peers at Bobby for a moment before smiling so bright it almost hurts to look at him. Blaine reaches his arms out for Bobby to hold him and Dean is both amused and insulted by the way Bobby looks like he'd sooner face down a wendigo than hold his baby.

...And crap. Since when did Dean start actually believing Blaine was his?

Suddenly, Blaine sneezes and Dean doesn't realizes he's moving until he's already grabbing him from Cas's arms and cradling him against his chest. It startles him and his eyes immediately flicker to Cas' expression, worried that he might be angry with him. Fortunately, Cas doesn't look the least bit upset. But there's a warmth in his eyes that's somehow more terrifying than an overprotective angel parent.

Sam snorts a laugh while Bobby says dryly, "Now that's just too adorable for words. But would someone tell me what's going on here?"

"Shut up," Dean growls at them. Blaine just makes a content little noise and buries his face against his chest.

"Perhaps we should find Blaine somewhere to sleep so we can talk," Cas interrupts. Dean, who is still horrified Cas changed Blaine's diaper in the backseat of the Impala (never mind that they covered every inch of the seats with a changing pad and towels they stole from the motel), takes this suggestion in stride.

The only problem is that Blaine latches his tiny fingers around Dean's shirt and refuses to let go. Sam teases him about it, so he retaliates by ordering him to go into the kitchen and make him something to eat. He gets the bitch look in return, but whatever. Caring for a baby-who-might-actually-be-his makes him hungry.

As Sam puts the bags of baby supplies away, Dean drops on the couch, Blaine dozing over his chest. Cas sits down on the couch too, forcing Dean to draw his legs up, and watches him hold Blaine like it's the most fascinating thing he's ever seen. Dean squirms under the scrutiny and distracts himself by running his fingers over Blaine's wild curls.

"So who does that baby belong to anyway?" Bobby asks as he wheels himself in front of the couch, studying Blaine curiously.

"Blaine is our son," Cas says proudly. Dean looks at him and can't help but think of a bird ruffling its feathers up to look more impressive.

Bobby's brow furrows in confusion. "Your son?" he repeats. "You and-...?"

"Cas and Dean," Sam replies as he steps back into the room. He's holding two plates of sandwiches and he reluctantly hands one to Dean, who immediately makes a grabby hand at it. It's a little difficult to eat over Blaine's head, but he figures that any crumbs that fall into his hair isn't going to hurt him.

"What?" Bobby looks at them desperately, as if begging someone to suddenly yell, "Just kidding! Haha! Fooled you!"

Dean shrugs and glances at Cas, who stares calmly back. "You did promise you'd explain where the kid came from."

Cas waits politely for Sam to cross the room and sit down in one of Bobby's wooden chairs before taking a deep breath. "My garrison and I were sent to Perdition in order to retrieve Dean's soul..."

The title comes from "Cough Syrup", originally by Young the Giant, later covered by Blaine Anderson (Darren Criss) from Glee.