Disclaimer: I don't own Life with Derek or its characters.

Switzerland on the Couch

Derek and Casey were fighting again. Edwin Venturi watched them. Really, his big brother and step-sister were better entertainment than anything on TV. Predictable as it was, terrifying as it was on those occasions when he and Lizzie got pulled into the carnage, he was never, ever bored watching them go at it.

He'd gotten here too late to know what had started it this time. It wasn't the remote, because they were in the kitchen and Marti and Lizzie were watching cartoons. It couldn't be something Derek had done at school to humiliate Casey, because it was a Saturday. At any rate, at this phase the argument had already devolved into insults. Derek was telling Casey she was hopelessly uncool. Casey was telling Derek he was an idiot. Soon—

Edwin leaned against the door frame. Yep. They'd started wrestling now. Casey pushed Derek. Derek got Casey in a headlock, pushed past her, ran past Edwin, into the living room, and up the stairs. "Derek!" shrieked Casey, hair flying out behind her, separating his name like she always did whenever she was really exasperated, which was always. Edwin knew Derek would be grinning upstairs, waiting for her to come barreling up after him so they could fight some more.

Casey ran past him, too. Edwin smirked, went to the fridge, grabbed a pop, and returned to the couch with Lizzie and Marti. Lizzie rolled her eyes at him in sympathy. Marti just kept watching TV. The three of them had learned to tolerate the constant fighting between their eldest siblings. It wasn't like it was going to stop.

Derek had always really liked irritating people, but his days had gained a new focus since the McDonalds had moved in. Before, his mischief-making had been…intermittent. When he felt like it, because he was too lazy to pull something every minute of every day. But when Casey'd come around, all that had stopped immediately. Admittedly, Edwin could see the appeal. Casey was organized, bossy, neat, and precise. That had to tick his sloppy slacker brother off. But what really made annoying her worth it was the reactions. Her dramatic, loud, angry fits were more fun for Derek than anybody else's in the house.

Not that they couldn't get along. Sometimes, something threatened both of them, or the family, and when that happened those two could cooperate to move freaking mountains. It made Edwin's dad and Nora angry, that they could get along and just didn't. Edwin had a theory, though.

It was kind of gross, because by now Casey and Lizzie were as much Edwin's sisters as Marti was. But Edwin guessed it was different for Derek. He'd been a teenager when the McDonalds had moved in. He'd taken Lizzie on, sure enough. Eventually. But Casey? Sure Derek and Casey fought like cats and dogs, except when they didn't. But all the time, whether they were scheming together or screaming at one another (well, Casey was screaming at Derek—Derek was usually laughing at Casey), they stood a little…too close. Now, Derek pushed and punched Edwin all the time, but Edwin thought it should to be different with a sister. Edwin sure didn't manhandle Lizzie the way Derek did Casey when they had their (rare) fights. The way Derek and Casey fought was just…weird, as well as entertaining.

Casey's door slammed upstairs, and Edwin heard Derek laughing. He smirked, a little disgusted, but mostly just amused. He looked over at Lizzie, who shared his theory.

"Think Casey'll ever figure it out?"

"I don't think Derek's figured it out," Lizzie said.

Edwin considered. "Probably not," he admitted. "Marti, give me the remote."