The thing about Donnie was that he never knew when to quit. He could be operating flawlessly on two hours of sleep and two-to-ten pots of coffee, and you wouldn't know it till he opened his mouth and tried to be a human being and all that came out was some form of "fuck off, I'm working" in varying levels of attitude, from 'pissy' to downright 'will set you on fire.'

Or, similarly, he could be at home, trying to put on a jacket before Casey's surprise birthday party – and honestly, who the hell did Casey's family think they were fooling – and missing the second sleeve four times; prompting Casey to bite the bullet and ask the question he'd been dying to ask since he walked through the door five minutes ago.

"Hey, D. Y'alright? You look a little… y'know. Terrible."

Sharp red eyes cut across the room to him, and Don opened his mouth – then shut it again, and blinked. Because tonight was Casey's twenty-first birthday, and Don never said shitty things on Casey's birthdays, and Casey wore that knowledge like a suit of armor.

"I'm fine," he muttered, and seemed to give up on the jacket. Which wasn't the best idea, since it was February. Casey frowned, and stood up, and Don sensed danger. "Really, I'm fine," he added quickly, backing up for every step Casey took towards him. "Just – I had a long day at work, and – "

But this close, it was easy to see Donatello wasn't going to make it to the party. He wasn't going to make it much farther than the front door – his eyes were glassy, and his face was a dull, burnt red – and something fierce and toothed came alive in the pit of Casey's chest.

"Jesus Christ, Donnie," he said sharply, cupping his face in one hand. And he didn't recoil at the packed heat rolling off Don's skin, but it was a pretty close call, and that just sealed the deal. "What the hell are you doing, you should be in bed."

"No way," Don said, and his expression folded into the ridiculously stubborn glower that promised a knock-down, drag-out fight every time. "There's no way I'm missing your birthday. I took some medicine, I'll be fine. I mean it."

Proving once and for all that Don, genius that he was, was also an idiot.

And the thing was, Casey's birthday wasn't a big deal. Hadn't been since mom died, really. He got a card in the mail from his sister, and his dad left him alone unless he was smashed, and he usually treated himself to a slice and a root beer from the dive down the street then called it a night.

Or, that's how it used to go. That was before April and the guys had fully adopted him, dragging him unresisting into their fold. And now he had a family of his own, one that was his, pieced together from the best parts of broken homes. He loved them more than he knew what to do with – and they loved him, too, he finally had that figured out. So for the last few years, his birthdays usually kicked ass.

But it had nothing to do with the places and the parties, and everything to do with the people. Obviously.

So Don was an idiot.

"Who are you calling?" Don said suspiciously, when Casey pulled out his phone. His eyes tracked Casey warily, and shot wide in surprise at Casey's quick, 'Hey, April.' "Jones, don't you dare!"

But he subsided into a coughing fit, one that seemed to fold him in half, which was what he got for getting so worked up in the first place, the moron. (Casey beat feet to the kitchen for a glass of water, anyway, because Casey was wrapped around two little fingers in this life, and one of them was most certainly Donatello's.)

And by the time Don drained the glass, and got his wheezing breath back, April had promised in no uncertain terms to 'take care of everything,' and 'be home in an hour.'

Don looked torn between fury and tears, and it was a neck-and-neck race but misery was gonna win out either way, and Casey literally could not handle waterworks without getting a little misty-eyed himself; so he shoved his phone into his pocket, and moved back into Don's orbit. Put himself close enough to get punched, but he wasn't too worried about that.

"You're being stupid," Casey said succinctly, taking Don's face in both hands. "You really are. I'm gonna give you a pass 'cause you're sick, and your brain isn't firing on all cylinders, but next time I won't be so generous."

"But it's your birthday," Don said, and he sounded so upset that Casey felt a pang deep in the soft, warm, pulpy part of his heart. "And now it's –"

"If the next word out of your mouth is 'ruined,' I'm gonna clock you. My birthday would have been ruined if my boyfriend passed out or puked or something because he's sick as hell and didn't tell anyone. But since that didn't happen – and since you're gonna shut up and be good and let me and April take care of you – then I got nothing to complain about."

"You could've just – I could've just stayed home, and you could've gone."

Casey was the one with two brilliant, beautiful partners to somehow measure up to and do his best to be good enough for, but nine times out of ten Don was the one convincing himself he was inadequate in this thing the three of them had. It showed itself in weird ways, and this was definitely one of them.

"I'm not even going to tell you why that's dumb," Casey replied, and he didn't mean for his tone to gentle so much, but there it went. "'Cause I know you know already."

Don leaned into him, blinking wetly, and then leaned a little more, and – yeah, okay, he was going down. Casey caught him quickly, and bore him to the sofa in a few swift steps.

"Stupid, stupid, stupid," he chanted, working Don out of his layers and wrestling off his shoes. Made a trip back into the kitchen to whip up a cool compress and weed out the thermometer, grabbed a bottled water out of the fridge, and took his haul back out into the living room. He was planning on setting up shop in the armchair, but Don's glassy eyes were open and following him; and wow, he was really sick, he looked even worse now that the act was over.

And without any conscious decision on Casey's part, he switched tracks. Ended up on the sofa with Don's head pillowed in his lap, tracing the cool, wet trails across Don's forehead from the compress with the tips of his fingers, and talking to keep him company, about class and the weather and the birthday wish he would have made on the candles of a cake. A wish he made instead on the dusting of freckles across Don's cheekbones that Don would swear up and down he didn't have, grinning when Don's face wrinkled in annoyance but he couldn't muster the strength to argue.

April found them that way forty minutes later, storming their shared fortress armed with two bulging pharmacy bags and no small amount of fierce determination. But her face softened on the two of them, and she only paused to close and lock the door behind her, and slip out of her coat and shoes; then she swept towards the sofa, bringing a crisp winter chill along, and sat on the edge of the coffee table. She slid cold fingers into Donnie's hair, and murmured something sweet and soothing, and then took Casey by the chin and kissed him in the proprietary sort of way that knocked his whole world spinning.

"Happy birthday, baby," she said, and then, "Scoot over," and Casey scooted. Let April bury her icicle toes under his thigh, and her hands under his shirt, because apparently Casey was nothing but a convenient space-heater, and complained the whole time while she giggled unrepentantly, just because he knew it would make Don smile.

And it did. And hell, Casey was smiling, too.