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He wasn’t even really supposed to find out.
That’s what Donnie’s been telling himself the past hour at least, pacing up and down his lab, near enough wearing holes into the floor with each quick stepped footprint he left behind with his obsessive worrying, he stops in his tracks and allows his eyes to flicker over towards his desk.
There’s an overflowing mountain of paperwork there resting right near the edge, dangerously so; nothing new in terms of how he decidedly ran his lab.
Organized chaos worked for Donnie.
But it was the four little petri dishes that were lined up beside the stack of paper, neatly laid out like damn weaponry, and Donnie feels his gut roll before tearing his eyes away and continuing with his circled lap as far away from the desk as possible.
He’d simply meant for the blood samples from himself and his brothers for an entirely medical standpoint. They lived in a sewer, they were off bouncing around on city rooftops breathing in god knows what all year round, on top of that naked. They were half reptilian. There had to be some pushback from all that.
So Donnie had managed to wrangle his brothers into his lab, unfortunately for him like herding a bunch of alley cats, they’d whined and complained and all about hissed at the idea of being poked and prodded with needles, Mikey especially.
And so Donnie had simply wanted to just run a check to make sure everything was running smoothly between the four of them. Nothing glaringly wrong or anything to worry himself over. Just… a simple, easy check up.
And then, enter Casey Jones.
He’d been bored out of his mind, spinning in slow circles on Don’s chair, rambling on about something mundane and useless, nothing but white noise to Donnie’s peripheral hearing, when Casey had stood up and stretched a leg out, face breaking into a grin, he’d exclaimed with an almost childish excitement,
“Hey, Dee! Guess who got a second growth spurt? Check this out!”
And Donnie had reluctantly swiveled around in his chair, a picture of absolute uninterest plastered across his face but Casey was either too oblivious to notice or he just didn’t care enough to mention it, he instead was pointing rather enthusiastically at the cuff of his jeans which, instead of resting around the bottom of his foot like they perhaps normally did, were now swinging around the tops of his ankles, clearly a touch too small for him.
Donnie huffs a dry laugh, one corner of his mouth tilts upwards into a sarcastic kind of smile.
“Are you sure that you didn’t just shrink them in the washer?” He pauses. “If you even know how to use a washer, that is.”
Casey just deadpanned him for a second before his expression was making way for something more smug. A real Casey Jones original look.
“Heh,” he’d chuckled shortly. “Maybe you’re just jealous that I might end up being taller than you.” He stops, as if considering something for a moment, tipping his head sideways, he drags his gaze up and down Donnie’s form a few times, making the turtle feel only just a little uncomfortable under his sudden scrutiny.
“How tall d’you think you’ll get, Don?” He questions him, as if he’s genuinely interested in such science.
Donnie shrugs. He was supposed to be working on Metal Head prototypes but since every iteration he’d been working on, and failing on, was just making his head hurt more and more, and so he supposed a little biology lesson with Casey couldn’t hurt.
Besides, he supposed that whatever actual science lessons Casey had ever received from school, probably had never stuck before, so he could maybe make an actual difference here.
‘Maybe’ being the key word.
“I’m guessing that the tall genes were probably borrowed from Master Splinter,” Donnie muses. “He said he grew a couple of inches after he mutated but from what he told us, he wasn’t exactly the shortest of guys when he was human.”
Casey barks a harsh laugh then, head thrown back, he’s narrowing his eyes into something darkly playful.
“So I guess Raph and Mike lost out on those genes,” he snides. Even Donnie can’t help but grin just a little bit. Sure it was bad brother etiquette to bring up one’s height, but they weren’t around to hear it. Plus, it was just a little bit funny.
“Probably,” Donnie tells him. “Though, it could just be turtle DNA. Without having a proper look at our molecular structure I can’t be so certain what gave us specific traits.”
It’s then that Casey stops spinning, pausing halfway across the room, he fixes Donnie with an entirely serious look, brows furrowed, he tips his head forward as if for emphasis on how real he’s being right now.
“Wait,” he says slowly, scooting the chair forward with the heels of his shoes. “You’ve… you’ve never actually checked your DNA out?” He asks, voice piquing at the end with disbelief. “Dude! And you call yourself a scientist, man.”
Donnie scoff, rolling his eyes, he tries to ignore the wah his cheeks feel just a tad hotter than before, he waves Casey off with a flap of his hand, dismissing him before saying,
“Yeah, well, it’s not like it was super easy to just get a DNA test, idiot. Maybe now with all these spare Kraang parts but even then, it’d take some time to set it all up.”
Casey’s eyes sparkle with something excitable yet dangerous. “But it’d be worth it?” He’s practically goading him at this point, pitching himself so far forward in the chair, it looks like he might just fall right off. “Right?”
And Donnie huffs a breath of air at the same time he reluctantly agrees and says right under his breath with disdain,
“Yeah. Right.”
And now here he was. That… stupid little conversation with Casey had worked itself into his brain like a damn parasite, coiled around him and relentless, whispering back his human friend's words as he’d tinkered with the blood vials and…
And he hasn’t meant to find out. Really, truly and honestly, he’d always had a slight fear of this kind of information thrusted upon him, and Kraang parts be damned, maybe that was why he’d never bothered to find out beforehand.
So… him and his brothers aren’t… really brothers.
He takes a sobering breath. Okay. So what? He’d always kinda ping ponged that theory around in his head for years.
What were the chances that a bunch of pet store turtles really came from the same nest? It wasn’t like they were ever wild animals, rescued and raised. No. They were bred specifically for little boys' bedroom decoration, a novelty purchase where the excitement of having a new animal to feed and look after would have worn off in a matter of days, and the responsibility of keeping them alive would fall upon a rather reluctant mother, if that.
Donnie knew that. He knew that turtles often came from larger nests than just four, and so he’d always toyed with the idea that they probably had other siblings out there, the non mutated kind, probably living out that same little boy bedroom life right now, if not already buried in a shoebox somewhere next to the old family cat.
But having the evidence presented to him like this, right in the open on his desk, so real and vivid.
It feels wrong. Like he walked in on something he shouldn’t have. He curses at Casey for ever pushing him to do such a thing but deep in his heart beneath his plastron he knows that this is a classic Donatello screw up. He made this mess.
Now he’s just gotta figure out how to clean it up.
Well, there’s no going back on the fact that he’s just going to have to accept that none of them are related. Not even through Splinter’s human DNA, there’s nothing there to indicate even the faintest of links that they could even be… cousins.
He moves back towards the desk, huffing a disdained sigh. He should call it quits and maybe draw up a game plan on whether or not he’s gonna tell the others about this but instead he can’t help himself, going over the results once more, moving a finger over the printed sheet that the computer had spat at him, he feels his brow wrinkle. He hadn’t even considered that.
So the human DNA part that was sliced with their turtle DNA wasn’t even entirely the same between them.
If it wasn’t so world rocking then maybe he’d find himself a little more intrigued rather than apprehensive.
They all shared the same amount of human DNA with turtle DNA but differently. Donnie had always considered the fact that they probably turned half human after the spill because Splinter had held them or touched them or something , but that surely couldn’t have been the case.
Splinter was turned into a rat first, before they’d had any chance to be part of the mutated gang. So… realistically, wouldn’t they have been half turtle half rat? Maybe it was a glaringly obvious plot hole in their origin story that Donnie had made sure to steer clear of in case of digging himself too deep of an existential hole, but now he’d already dug it and fallen right in, and the evidence was clear.
It made sense now that they’d have picked up their human DNA from other people who’d probably handled them in the pet store.
The cashier, the store workers, kids that didn’t know not to reach in and grab. There were probably people walking about New York City right now not having the faintest of clues that they’d lent their skin cells to help mutate a bunch of giant walking, talking ninja turtles, all because they’d probably picked up a baby turtle out of a glass tank and held it for more than a second almost twenty years ago.
That explained the different traits. Why Donnie was taller and why Mikey had freckles and their eye colors being different. Donnie still clings to the hope that he borrowed his brown eyes from his father. He’d always secretly wished upon that, even if it did used to make Leo a little jealous.
He sighs, dropping into his chair, it squeaks under the sudden weight, he stares uselessly at the dishes and the paperwork like it might just combust right there on the spot and he wouldn’t have to deal with this anymore, the evidence inconclusive, he could go back to not knowing anything about any of this.
But for once, nothing in his lab sets itself on fire. Everything stays exactly where it is, like it wants him to know, and his chest heaves with another loaded sigh.
He could just pack this stuff away and never let on to anyone ever. There’s absolutely no way he’s entrusting the information with Casey alone but…
He’s awful bad at hiding secrets. And this one feels pretty weighty to bear alone. He draws in a breath.
Okay, so, Leo is like their sensei now. Leo is their leader and… well, he’s their older brother. Even if not by blood, he’s always held that title pretty proudly. And after this, maybe a little more.
He blinks at the samples. There’s no way he’s gonna go ahead and test their actual ages. If he takes away Mikey’s little brother privileges he might just throw a fit and cause some time travel hooha just to ensure he remains the baby of the family.
So despite the little nagging desire to figure out who was older between himself and Raph, he keeps that side of the experiment at bay.
Running a tired hand down his face, he realizes what he’s gotta do. He stands and makes his way to the dojo. It feels like a funeral march.
Leo is there alone. No surprise, Raph and Mikey are off goofing around somewhere deep in the sewer tunnels, having left a good few hours ago, their departure had been followed by the sound of rattling paint cans and Mikey’s voice excitedly booming as he’d explained to his brother the, quote on quote, sweetest spot he’d found for their work, and Donnie knew once they found a good place to spray some paint, they could be out all day.
So, good timing on both their parts, he supposes.
Leo notices the other turtle standing idle at the doorway, he pulls himself out of the kata he’d been practicing and smiles towards him.
“Hey man,” he says it so easily. “You okay?”
Donnie nervously fiddles with his wrist wrappings.
Should he even tell Leo about this? What good does it do? What does it gain to their family?
But he’s already here now and he’s not much of a good on the spot liar so the words just kind of rush right out of him all at once like verbal vomit.
“Uh, you know that blood sample I asked you guys for a couple of days ago?” He says.
Leo’s face almost collapses in on itself with how fast a frown appears on his expression.
Donnie’s heart leaps into his throat. Oops. He had told his brothers it was for medical reasons and standing here looking like he was about to tell Leo the absolute worst probably hadn’t set him in the right direction emotionally.
He waves his hands uselessly and chuckles a nervous laugh that bubbles out of him involuntarily.
“Nobody is sick,” he’s quick to assure him. “Or dying or anything like that.”
Leo’s shoulders drop about twenty feet and he almost looks like he wants to reprimand Donnie for scaring him so bad.
“But, uh, there’s something maybe you should see,” he finally tells him.
And Leo looks a touch hesitant at first. But he nods, and his mouth lifts into the faintest of smiles.
“Um. Okay? Sure. Lead the way, Dee.”
***
Leo is there standing before his desk, staring at the results with the same fierce intensity that Donnie had.
When he came into this lab, he was under the impression that he had three brothers. Now he stood here, swallowing the rather large pill that Donnie had unceremoniously stuffed down his throat that they didn’t really have any brothers.
None that were mutant ninjas at least.
“I know I shouldn’t have tested it,” Donnie says meekly, voice feeling too loud for the quiet, but since Donnie had explained it all, Leo’s yet to have said a single word. “I kinda regret it now but… you know regrets are pretty useless things.”
Leo’s head swivels around to meet his, there on his face is the slightest of sympathetic looks. Brows curving, lips inching into a smile, he tips his head sideways, and tells him,
“Donnie, regrets are nothing if not opportunity for growth and going forwards.” He looks back at the dishes. “So… maybe this is a few more steps forwards than anticipated but, hey. Listen.”
Donnie does.
“It doesn’t really change anything.” He says it so sternly, like it’s absolute fact, and Donnie feels that, all the way down into his bones, he knows that Leo’s right. These facts, these scientific jumbles of letterings and scraps of data and such – it's just that.
Family is… well, Donnie already knows what and who his family is.
“I know,” he says with a breath, reaching a hand up to rub the back of his head rather nervously. “I thought it’d be a fun little experiment but I guess I wasn’t really too focused on the outcome had it been negative.”
Leo blinks. “It’s not all negative,” he says pointedly. “I think we’re past the days of those scrappy fights with one another. Even Raph, believe it or not. This won’t get in the way of that, I’m sure.”
And that was exactly what Donnie was afraid of. Handling this information between his brother and himself, he knew it was perfectly shaped gunpowder to escalate any kind of argument that sparked between them.
All it would take is some petty fight and for one of them to reach their boiling point, to clench their fists and bare their teeth like wild animals and scream out, ‘you’re not my brother!’
He swallows thickly; it feels like there’s a knot pressing tight against his throat.
“Besides,” Leo muses, shifting his weight onto his good leg with practiced ease. “It’s not like we have to tell the others this, right?”
And Donnie goes to open his mouth, perhaps an instant agreement resting there on his tongue because yeah maybe keeping it a secret from their most emotionally explosive brothers might work in their favor.
But all that gets flushed down the drain when the lab doors open with a heavy creak and Raph and Mikey are standing there in the doorway looking curious, breathless and covered in paint.
“Tell the others what?” Mikey asks.
So it appeared their little outing had inevitably turned into a full on paint fight and now there was no denying what they’d just inevitably overheard.
Donnie pins Leo with a rather desperate look, and the other turtle heaves a dejected sigh and turns to their rainbow coloured brothers still standing there awaiting an answer, he’s already moving past them into the kitchen, calling out behind him in a flat voice,
“Family meeting in the kitchen.”
***
Donnie is handing Raph the paperwork whilst Leo runs a wet cloth over Mikey’s shell, working through the grooves to get rid of the yellow paint that Raph had splashed all over him.
Though, when Donnie looks up, the eldest isn’t really paying too much mind to his cleaning task, instead his gaze nervously flits between his brothers, as if gauging their reaction with each passing second.
“I don’t get it,” Raph says bluntly, slapping the paper back down against the table, sliding it towards Mikey again who just blinks at it.
“Like, what’s the point of this?”
Donnie swallows, perched in his seat he stuffs his hands underneath his legs, only because he knows by the end of this conversations he’ll have nothing but shreds to show for his wrist wrappings what with all the picking at them he’ll know he’ll do.
Lucky for him, Leo steps it, slinging the wet rag into the sink, it’s clear that the paint on Mikey’s shell can wait for now.
“There isn’t any,” Leo tells him. “But it wasn’t fair for Donnie to know by himself.” He shoots his brother a sparing look. “And like I told Donnie, this doesn’t change anything, right?”
There’s a heavy silence settled around the room for a moment, and Donnie fears that maybe it’s like pressurized air before a bomb goes off, sending shrapnel and debris flying everywhere, he knows Raph isn’t against blowing up in such a short amount of time.
But he doesn’t. He just glares at the paper, much like Donnie did and Leo and, ha, maybe they’re more alike after all.
“So… we’re not even like, a little bit related?” Mikey says in a small voice, eyes not bothering to lift up from the sheet in front of him, Donnie knows he can’t possibly be reading it; full of numbers and symbols and all kind of sciencey junk that’d be like reading Chinese to him, his heart sinks just a little to know why he was perhaps avoiding full eye contact.
He sucks in a short breath, steeling himself he says,
“Well. Yes and no.” Mikey lifts his head upwards then. “Like I said, it wasn’t Splinter’s DNA that gave us our human genetics. Just… random humans that we’d come into contact with perhaps that day or the day before.”
Raph hums. “Makes sense. We’ve seen how the mutagen works — you're basically spliced with whatever you’ve touched beforehand, right?”
“Right,” Leo nods. “We just never questioned how it worked with the rat DNA being thrown in there.”
Mikey laughs weakly, sliding the paper away, he folds his arms across the table, leaning forward he settles himself there. “Ha. And a good thing too. Imagine what we’d look like with whiskers and big, pink tails.”
Donnie manages a small smile, just for Mikey’s sake.
“Also kinda makes sense that Sensei wasn’t turned into a giant turtle,” Raph then shrugs, sounding his words out as if unsure. Donnie sits up, perplexed, he blinks across the table to his brother.
“Hey.” He says with short surprise. “I hadn’t even thought of that.”
Raph’s expression twists itself into something smug and playful. “You can’t be the brains of this operation all the time, Dee.”
Donnie snorts. Okay, so brotherly banter was still in full swing. At least he hadn’t completely decimated that yet.
“And,” Mikey pipes up, garnering everyone’s attention at once. “Like… we knew that Sensei wasn’t like, our real dad, right?” He blinks. “It didn’t stop us from loving him like one.”
Oh Mikey.
“So it shouldn’t stop us from loving each other like brothers,” he smiles. “Like we’ve always done.”
It’s a touching moment until Raph scoffs and makes a gagging noise. Despite that, Donnie still grins.
“This is so cheesy I think you’ve put me off pizza for life, man,” he groans rather dramatically.
Leo gives him a playful shove, drawing a laugh out of him, the anxiety squeezing around his heart seems to settle just a bit, watching his brothers, his brothers still act the same as they did yesterday. And the day before and all the days before that.
Mikey then sits up, like a rocket up his ass, eyes wide and bright and full of idea, Donnie braces himself for what is to come out of his mouth next.
“Oh my god!” He says, entirely serious. “You know what this means?”
Leo looks at his brother and Raph just rolls his eyes.
“This means that your mama jokes are like, totally on limits now!” A laugh bubbles out of him, tipping his head back, he’s well and truly tickled himself.
Leo shakes his head with dismay, but the faint smile that ghosts his lips isn’t lost on Donnie.
Raph groans in retaliation.
“Mikey, you are such a knucklehead. Seriously, what do you have like a brick for a brain?”
Mikey snorts a laughter, eyes crinkling with glee, he smiles at his scowling brother.
“No, but your mama does! Ha!” He squawks an obnoxious laugh, pitching himself forward in his seat. “Get it?! I can totally say that now cos we don’t actually have the same mom!”
Leo gently pulls Mikey back off where he’d sprawled himself halfway across the table, reaching for the rag again, he shoots him a reprimanding look.
“First of all, that wasn’t even clever or funny and second of all, we don’t even have moms so what different does it—”
Mikey pouts, pulling out all the stops, it’s clear to Donnie that this new information hasn’t deterred his brother in any way possible. In fact, it seems to have spurred him on to act more heavily on his annoying younger brother duties than usual.
“Hey. You can’t be mean to me,” he says in a thick voice. “I just found out I’m adopted, dude. Lay up.”
Donnie smacks a hand across his forehead. “We’re all— ugh. Never mind.”
He shared a glance with Leo. “Hey. At least now you know you’re not at all related to him,” he smirks playfully.
That earns a laugh out of Raphael, jeering a finger in his face. “Ha. I think we’re all relieved on that front.”
Mikey swats his finger away and allows himself to sit still long enough for Leo to keep scrubbing at his shell.
“Big meanies,” he says with absolutely no heat to his words whatsoever. He twists around to face Leo, whatever patience he had to sit still has already run thin. “Hey Leo, is this gonna take long? I have to beat Raph at like, everything to prove I come from the stronger turtle pack, starting with the pinball machine he thinks he’s a god at.”
Leo huffs a laugh. He keeps on scrubbing. “Just sit still you menace.”
Donnie watches over his brothers as he collects his things, he wordlessly removes himself to head back to the sanctuary of his lab, leaving the playful banter behind in the kitchen down to Leo to keep under control, he dumps his stuff back on his desk, along with the rest of his clutter, he finds himself smiling.
Mikey had a point: Splinter was never their real father. But April was never their real sister. And Casey wasn’t their brother by blood.
So what was the difference? Donnie already had bucket loads of experience in mismatched, stitched together, rag tag team of families. He already had one, and if anything, knowing that they were as strong as real brothers (whatever real brothers were) it was all the more admirable that they’d stuck together for as long as they had.
They’d been placed in that tank together all those years ago, maybe with a bunch of other helpless turtles that’d been picked off by oblivious pet owners, leaving just the four of them to be purchased together.
Science was a pretty cool thing at certain times.
But fate and family was a million times more impressive to Donnie any day.