This chapter was made on November 11th, 2017. It has been rewritten since November 17th, 2020. I am now a more capable writer who wishes to rewrite their previous work. Some details might change, old fans will notice, so some comments may not make sense.
You may notice the writing style change next chapter - I may have not gotten to that chapter yet, and am working on it currently. Sorry about that!
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Leonardo glanced at the television as he walked past, watching in mild amusement as the characters on the screen danced about, trying to knock the other onto zero-health. Raphael was laughing, a first in a while, Leo assumed. He sounded happy and relaxed. Michelangelo was squealing as his character was beaten again and again, only getting in a few punches to the ever-growing onslaught coming from the red-banded turtle.
"Hey Leo!" Mikey whined, drawing the older turtle's attention towards him again, deep blue eyes meeting baby blue. The younger smiled; "Come beat Raphie - he totally cheated and I'm out of lives!"
The leader was close to declining, but from the glare from Raphael that he was sending his way, he thought otherwise. Hopping over the sofa to sit next to the youngest, he grinned. "Okay - where's the controller?"
"Hell yeah Leo!" Mikey cheered, handing him the controller quickly - they'd been made to work with their three fingers, so Leo had no problem easily getting used to this games programmed controls (thanks to Donatello remaking it for them after Raphael had rudely shattered the disk), and soon, he to was laughing as he took on the strongest turtle's character.
...
Donatello couldn't believe it. These results... no. He shouldn't have looked - he should have just left it as it was. But no; he took Leonardo's suggestion and found a loophole in their family system. Surely he should've seen this coming - right? Surely...
...
"Guys..?" Don said softly, voice barely making a dent among the sounds of Mikey chewing as they ate dinner, Raphael following close behind in the sounds of slurping and gulping. The purple-banded turtle shuddered as all the eyes turned on him. "I have something to... say."
There was a moments silence as they waited for him to speak. Don took in all their faces; Leonardo was ever calm, his kind, blue eyes speaking wonders to his soul, Michelangelo was still bouncy, not caring about the tenseness that had come over the room. Raphael was a different story.
"Spit it out, idiot." Raph muttered, eyes ablaze. Clearly he hadn't won the videogame match that Donatello had heard him playing against Leonardo earlier. "We ain't got all day."
Donnie's mind stuttered, as did his words. He would have never imagined that he would have to spill this information out. He could keep it in instead, keep it to his dying grave, but alas, his brain just couldn't function like that. Besides, Raphael would probably beat it out of him. "Okay... Okay. Raph, uh, put us all in age order."
Raphael snorted, raising a suspicious eyebrow - "Leo, me, you, Mike."
"I... Leonardo gave me the idea to check our DNA from our blood banks-" He turned to Mikey, "Meaning looking into how our body works, Mike." He got a confirming nod from the smaller. "And, it turns out, mutants DNA can show their age, as well..."
"So what? You're gonna tell me Mike's the oldest?" Raph chuckled, and Don caught sight of him twirling his finger around his Sai's blades. He was nervous. "If so, afraid I'll have ta kill him."
"Raph!" Mikey shrieked, and Don put his fingers to his tender head, sighing heavily.
"Guys, c'mon." Leo said, shifting in his seat to appear to be paying more attention. Donnie's heart stuttered as he imagined how that kind look would change once he found out the truth. "What's up, Don? What did you find?"
"I ran... ran a bunch of tests, right? To check different things - like turtle-species, a-and I decided to try looking into our ages. Raph-" His gaze turned back to his immediate older brother. "You're the oldest. Leo... Leo's the youngest, actually."
There was a dead, foreign silence that sprung upon them. Even Mikey had stopped eating, mouth agape in silent surprise. "W-What?"
He swallowed the building lump in his throat, before steadily repeating. "Leo's the youngest. Then-then Mike, then me, then Raph."