Birthday celebrations hadn't been a big part of Isaac's life before he had come to live with Derek. The first time the pack had celebrated with cake and presents for Erica's birthday it had been a shock not only for her but for Derek and Isaac, and even Boyd, whose own birthdays had gone nearly forgotten for so long.
It no longer surprises Isaac when, on someone's birthday, Stiles shows up with streamers and balloons, or when Derek trudges in behind him with a cake and a wrapped package or two, looking every inch the unamused boyfriend who has been coerced into helping.
It isn't any more surprising now, when it's his own birthday they're setting up for, but that doesn't stop the warmth that curls in Isaac's chest when they kick him out of the main living area so that it will be a "surprise."
They all know it won't be, but Isaac still goes willingly, scooping up Scott the cat and heading to the bedroom that is the only space really partitioned off from the rest of the loft.
Isaac is mostly asleep, book resting on his chest and Scott curled next to his head, when he's woken by the noise of the others trudging into the loft. They're a small group, but they're loud when they're happy, and Isaac can hear the chatter of voices and the scuffle of feet. He doesn't move yet; he closes his eyes and listens to the sounds of his friends—his family—gathering to celebrate the fact that he exists.
Eventually there are footsteps outside the room, and Stiles's voice drifts in telling Isaac that he should come join them in the living room. Isaac takes another moment, turning his head to yawn into Scott's fur before he abandons the bed to the cat and rolls himself to his feet.
The whole group is gathered when he emerges, party hats strapped to their heads and something that looks like black forest cake covered in burning candles on the table in front of them. The moment Isaac is in their line of sight, Stiles says "now" and they break into a round of "Happy Birthday" that is actually rather less awful than one might expect.
"Thanks, guys," Isaac says when they're done singing. He steps forward, watching the candles flicker on the cake for a few seconds before he closes his eyes and thinks of the one thing he most wants. When he opens his eyes, Scott is looking at him—they all are, really—but Isaac meets Scott's gaze and the connection doesn't break even when he leans over and blows out the candles.
He's mobbed with hugs just moments later, arms wrapping around him and clapping him on the shoulder, and kisses pressed to his cheeks—there's really no sense of which limbs are whose, and it really doesn't seem to matter (though he does wonder briefly whose hand it was that grabbed a handful of his ass in passing).
When they're all satisfied that Isaac has been hugged enough for the moment (and there will surely be more hugging later) they divvy up cake onto plates and the whole pack of them pile onto the one short couch and pair of chairs that make up the living room. They smoosh together, sitting half on top of one another and talking happily. It would be just like it always is when they're all together, but the topics of conversation never veer to alpha attacks or crazy teachers, and for a moment it manages to feel like they don't have to worry about anything besides not making themselves sick on too much junk food.
Isaac is mostly happy to listen to the others talk, curled up at the end of the couch with Derek next to him, and Stiles occasionally kicking him lightly with the foot he has draped across Derek's lap. He's even happier when the cat appears from the other room and immediately makes himself comfortable in Isaac's lap.
"Hi, Scotty," he murmurs. Both Scotts—human and feline—lift their heads to look at him, and Isaac can't help but grin at the way they respond the same way when called.
Scott watches him with the cat for a few moments with a soft, lopsided smile on his face, before he climbs to his feet, calling out "Present time!" before he disappears out the front door of the loft. Isaac frowns in confusion, watching the door for his reappearance until the others distract him with gifts.
Isaac is just looping the scarf Lydia bought him around his neck when suddenly Derek and Stiles shift beside him all at once. Derek stands, rolling his eyes when Stiles holds out his cake plate hopefully, but dutifully heading over to the table to refill it anyway. "Thanks, Pookie!" Stiles calls, voice pitched high and completely over the top, and eliciting a grunt from Derek.
The couch dips beside Isaac, and he turns his head to find Scott there, having returned from wherever he went and grinning widely at him. There's a box with a giant bow on it sitting on the floor between their feet, and the cat is sniffing around it looking put out. Isaac goes to grab him, but the cat scurries out of his reach and Isaac grabs for the box instead. "Happy birthday," Scott says when Isaac has it balanced on his lap.
"Thanks," he says, pulling off the bow and tugging at the suspiciously loose flaps of the wrapped box. When Isaac gets the box open, he barely contains an actual squeal, reaching immediately into the box with both hands. Curled up in one corner of the box is a little black kitten—not quite as small as Scott was, but still tiny enough to sit in one of Isaac's palms. Isaac immediately starts talking to the kitten, holding it close to his face and chatting at it while the others coo over how cute it is.
"He's perfect!" Isaac says, looking over at Scott, "thank you, Scott." And then, hands full of kitten impeding a hug, Isaac leans over and pecks a kiss to Scott's cheek in thanks, pulling back the next second and looking for any excuse to focus on something else while his own cheeks burn with embarrassment.
He ends up searching for Scott the cat, wanting to introduce him to the new kitten. The others are talking around and over Isaac while he twists to look for the cat, and he barely hears Lydia asking him a question when he spots the cat prowling towards the remainder of the cake on the table, looking about ready to pounce.
"Derek!" Isaac calls, pointing his elbow—hands still cupped around the kitten—towards the table at Derek's side. He watches Derek turn quickly and grab the cat up off the table with one hand. Scott curls happily into Derek's arm and the man hands off Stiles's second slice of cake to use both hands to hold the cat.
"… name the kitten Derek?" Isaac hears Stiles's voice say, slightly muffled around a bite of cake. He refocuses, looking to his left to find Scott laughing hysterically and Stiles giving him an odd look.
"Huh?" Isaac says, feeling lost.
"I mean, I get using Scott as a name given the whole," Stiles waves one hand in the direction of Isaac and Scott where they're side by side on the couch, "but Derek?"
"What? I didn't …" Isaac doesn't finish the sentence, still not sure exactly what's going on.
"Well, I mean, I guess he is still your alpha and all. And besides," Stiles tilts his head and looks at the kitten, "he does sort of look like Derek, doesn't he?"
Isaac feels like he's slowly connecting the dots. He stares down at the little black kitten where it is sitting in his hands, staring back at him with an unamused look. When Isaac glances up, he sees an almost identical look aimed at Stiles, who grins back at Derek until the glower softens into an affectionately resigned expression.
"There is sort of a resemblance isn't there," Isaac says.
"So you're actually going to name the kitten Derek?" Lydia asks, seeming to find the idea ridiculous.
Isaac contemplates for a minute, watching Derek's eyebrows lower again at the suggestion, and then grins and nods once with a "yup," setting Scott into another round of howling laughter.
Derek tries to fight the comparison between himself and the kitten, but the name turns out to be too apt to fight. Derek the kitten is a dark, bristly little thing: independent and proud but cuddly and protective once his trust has been earned; more than once he tries to protect Isaac from harm, hissing at the perceived threat of the lightning and waging a one-kitten battle against the vacuum cleaner.
Neither of the Dereks has any chance of winning their fights, but in the end it doesn't matter because the fights that do matter—the ones to keep their little family together—are the ones they somehow always manage to win.