He didn't even remember when he started calling them his brothers.

It wasn't intentional. He knew that for sure. Casey would have remembered deciding on the term. He didn't throw around family terms loosely. It wasn't in his nature. He knew when he started calling them friends; that was easy. Fighting together solidified that easy enough for the lanky teen. But calling them brothers? The moment escaped him.

Either way, once he started, he didn't even notice. The words flowed off his tongue like the term was natural. Like it belonged. He used it all the time. At practice. ("Hey Paul! Look at this shot my brother taught me") At school. (My brother has been tutoring me in math, Ms. Lois. I didn't cheat. Swear.") While on the streets, alone, patroling. ("You better watch it! My brothers are scarier than I am!") He didn't even think about it. Without even being aware of it, he had taken upon the Hamato siblings as more than brothers in arms. They'd become just his plain old brothers.

And like usual, this fact didn't hit Casey until someone pointed it out.

It was a normal day in the lair. Don was holed up in his lab, Mikey was training for once and Raph was busy "doing stuff" (which was knitting Casey a sweater for his birthday, but that was a surprise for later). After a long day at school, Casey had decided to go in the lair to play some video games. It was easier just to head straight there when he planned on patrolling later in the night. Because everyone else was busy, Leo had become his opponent for the latest version of "Fighter Stars 77: Evil Death." Leo was kicking his ass, so when he'd gotten a phone call from one of his fellow hockey players, he'd been thankful to pause the game. Well, at first.

"I can't come hang out, Paul," Casey said, his eyes still on the television. His character was dangling off an edge of a cliff, damage in the red zone, looking particularly worse for wear. Leo's character, on the other hand, was in pretty good shape, damage counter still in the bright green. Casey found it cruel that Leo could beat his ass in the digital world along with the real one. Especially when his fingers were almost too big for the buttons.

"Why not, man? We got some sick plans" Paul was one of those upperclassmen who seemed to be determined to make friends with all the younger students. Casey appreciated the effort, he really did, but he really didn't have any desire to join Paul and his gang for Friday night beer pong. He had better shit to do. World saving shit. Casey glanced at Leo who rifling through the Space Hero comics Casey brought back. It was the latest issue, and Leo's eyes were almost glued to the page. Knowing him, he'd read it three more times after Casey left. Casey cleared his throat and turned his attention back to the call at hand.

"Because I'm hanging out with my younger brother, that's why. Sorry, man." He clicked the disconnect button before Paul could protest. He really didn't want to drag this out. It was time to get back to gaming. Sweet, sweet, gaming.

It was only when he saw Leo's incredulous expression that his words sunk in. Brother. He'd called Leo his brother. While Leo was present. In actual words.

Screw his rising grades. He was an idiot. Grade A+,idiot. If there was a class for social skills, he would have flunked it right then and there.

"Casey?" Leo said. His voice was soft, almost nervous. Casey looked down at the eldest turtle. Leo wasn't looking at him, instead focusing on the floor. Like he was afraid of what Casey would do if he looked him in the eye. He had entirely forgotten about his comic. It was weird to see from a guy who was so confident. Almost wrong. It confused him for a bit before everything fell into place.

Casey felt his nerves drain out of him. What had Leo thought when he saw Casey freak out by dropping the "B" word? It probably hadn't been encouraging. Did Leo think he regretted the words, or something? That if he looked at Casey, he'd take it all back?

Never. He meant every word. Every last one.

Casey was suddenly reminded of just how young Leo was. The kid had gone through God knew how much in the last year. He could use a little reassurance. Casey could do that. He threw his arm over Leo's shoulder, taking the turtle by surprise, and pulled him in. He lifted his fist to Leo's head and gave him a noogie. It was a little odd since Leo had no hair but he went for it anyway.

"Don't think you can distract me, man. We got a game to play." He pushed Leo away and lifted back up his controller. He thought about leaving it there, but decided to press on. What did he have to lose? The moment was awkward already. "You ready to get your ass kicked, little brother?"

Leo's eyes widened for just a second. Just enough for Casey to catch the surprise. Then the blue mask turtle smirked, smirked wide and picked up his controller as well.

"You're on, Jones."

Leo did, in fact, end up kicking Casey's ass to the curb. Which was to be expected. They didn't speak of phone call after that, leaving it as a distant memory. But Casey still kept on referring to the turtles as his brothers. Even when they were there to hear them. And this time, he was fully aware he was saying it.

It was only a month later that he realized that they'd started calling him brother too.