Big Brother by AndromedaMarine

Detective Javier Esposito watched from his desk as Richard Castle said something that made Kate smile. For a few moments he let the case file in front of him go unnoticed, as he observed the writer and the detective share a bond that neither would admit (well, Kate wouldn't but Castle would be glad to do just that). Javier pushed the stray thought from his head and used unpolluted detective skills to go through different scenarios in rapid-fire succession, each involving how the writer/detective relationship (if it could be called such) would eventually collapse, implode, explode, be destroyed, end violently – and on, and on, and on.

Esposito stopped all motion as he watched Castle lean down from his seat atop Kate's desk to whisper in the detective's ear. When he pulled back Javier noted a distinct expression that wasn't entirely clear – it registered neither as overly flirtatious nor as boredom. Esposito drew from Kevin Ryan's vocabulary and designated Castle's features as "smoldering." Not that the word would come up in everyday conversation with the writer, nor would Javier ever admit to using it to describe him.

What happened next made a knot coil in the pit of Javier's rock hard stomach.

Rick and Kate both stood, and the former held the jacket open for the latter. After Kate stepped into her leather coat she turned around, and was caught by surprise when Rick kissed her. The kiss had landed too far from her lips to be considered forward, yet too close to her ear not to be. Javier's fingers clenched over the paper he'd been resting his hand on, and shot daggers at the writer. Ryan distracted him with a tap on the shoulder.

"If I were a profiler I'd say you look jealous."

"Not jealous, protective. Did you see what he just did?"

"Yeah, he kissed Beckett. Means that the Captain probably won the bet."

Esposito spun the chair around and looked up at his partner. "Sometimes I wonder about you, and whether you're really in touch with reality." He picked up the case file again, but glanced back at Castle and Beckett to satisfy his impulses. "I swear..." he didn't finish the sentence.

Ryan leaned against the edge of Javier's desk. Practically reading his partner's mind, he said, "Well if I were you I'd make it quite clear just what I intend to do to him if he does."

Castle made to leave following Kate, but a holler from Javier made him turn around. "Yo, Castle, wait a second. I've got something to ask you."

Richard shrugged to Kate and made his way through the bullpen to Javier's desk. "What's up?"

Javier noted that Kate was waiting for the author. He stood, making himself only two or three inches taller than Rick. "Do you understand what I mean when I say that she's my sister?"

Rick glanced at Kevin for some explanation, getting none. "Um, I don't think so."

"It means that I'm her big brother. Do you know what that means?"

One shade of color melted from Castle's face. "That I do."

"Then it goes without saying, though I'm gonna say it, that if you do anything, anything at all, to hurt her, you've got a lot of powerful people to answer to. Just for argument's sake, that list starts with me, includes Ryan here, Lanie, the Captain, Agent Sorenson – yeah, you remember him – all the way on up to your 'friends' the mayor and the commissioner."

Castle gulped.

"And it doesn't stop there. While Lanie would probably find some conveniently untraceable way to make you not a bestseller, I wouldn't make you a martyr. At least not immediately." Javier stopped to examine the author's now oyster-colored face. "If you choose to pursue some sort of relationship with Beckett, that's your doing. But we're here to look out for her, to make sure she's safe and unhurt. Don't make me go all big brother on you."

Kevin jumped in to ease the terror showing on Castle. "We're glad that she's happier, because she has been happier since you started shadowing. It shows in her work and her enthusiasm. Plus the espresso machine helped. And it's nice to not be the one she's yelling at once in a while."

Javier shot Kevin a look that said, don't encourage him.

"I know for a fact she hasn't been this happy for a long time. So if you do make her happy, you better hope it doesn't blow up in your face."

Kevin jumped in again. "We're not threatening you, per se, just making it clear what to expect if things don't go as well as you may hope."

Javier crossed his arms and nodded his head once. "This stays between us, Castle, you got that?"

"Yeah, oh totally yeah!"

Detective Esposito seemed pleased, relaxed. "Good. Now when she asks you what this was all about, you're gonna tell her, in complete honesty, that we were asking if you and her want to go to a baseball game next Saturday, because that's exactly what we're asking."

For a moment Castle looked confused. "Okay, so you're really asking if we want to go to a game?"

Kevin nodded. "Seattle Mariners versus the Mets, New York home field advantage. Seats with Joe Torre, if you can manage to use your connections to that advantage."

Castle smiled. "Consider it done."

Javier nodded again, and indicated that he was done with the author. He turned to Kevin once Castle had departed. "You think I laid it on him a bit too thick?"

Kevin shook his head. "Nah. He should know what he's getting into."

The two partners watched in silence as Rick returned to Kate, as Kate smiled widely at them after hearing the news of the game, and as Rick unconsciously put a hand on the small of Kate's back and guided her to the elevator doors, with not more than one or two inches separating them.

Javier sat back down, letting a sigh escape. "I've only had to make that speech twice. And the first was to Sorenson."

Detective Ryan made a noncommittal noise. "I'd say it's a perfected speech, and it'd be nice if you never had to make it again."

"Amen to that."