The first time they get caught by his daughter, it's mortifying.

It happens while she's home for Thanksgiving. They've gotten used to being alone in the apartment. Well, Martha is there, but she mostly makes a big deal about giving them their privacy, always retiring to her room at a decent hour. She's even taken to announcing herself every morning before descending the stairs after she got an eyeful one day—Kate and her son, almost naked (definitely getting there), pressed against the stove.

So maybe they've become a little lax, but when it happens, when Alexis catches them—Kate wants to crawl inside herself and die.

She was on tentative, friendly footing with Alexis after a few care packages and a night when Kate showed up at the dorm during mid terms and forced the girl to take a break and have lunch with her. It wasn't as awkward as Kate had feared. The girl was easy to talk to (she was a Castle, after all) and Kate had let herself begin to hope she might actually have a real friendship with Alexis someday.

But now. Oh God. Now this.

Kate got back from the precinct late. Castle had left pretty early so he could spend time with Alexis and when Kate walked into the living room, fresh off a newly solved murder, and found Castle sitting on the couch reading a book, looking so handsome in his blue shirt, open at the collar, sleeves rolled up—

She got a little carried away.

Castle looked up from his book, caught sight of her in the foyer. She had no idea what her face looked like, but judging by the way his eyes darkened about three shades, she guessed it must've been all over her face—how much she wanted him.

He began to stand up, but she walked over and pushed him back against the couch, pressed a knee to either side of his thighs and sank down into his lap. He groaned softly, reached up to grip her waist, and his hands were so large and warm against her and he smelled so good, felt so good—

Yeah, she definitely got carried away.

Alexis finds them with her tongue down his throat, his shirt half-unbuttoned and her hands inside. His hands are gripping her ass, pressing her hips firmly into his. At least Kate still has her clothes on. That's something.

Alexis lets out a muffled yelp of surprise and spins around, sprinting back up the steps to her room. Kate watches her go, a little stunned, then turns back to Castle and groans at the sight of him—hair mussed, lips smeared with her lipstick.

She reaches out to wipe it off, before leaning forward and burying her face in his neck. She's scared to look at him. She hopes he isn't mad.

"Kate," he murmurs into her ear. His tone is light, laughing almost.

She lifts her head to look at him, feeling bewildered and so embarrassed she thinks she might die. Oh God. His daughter caught them. Caught them making out like teenagers on the couch. She was never, ever going to get over this. Ever.

"Kate, it's fine."

"Castle," she hisses, smacking him lightly in the chest. "That was your daughter. Your daughter caught us practically dry humping each other on the couch and all you can say is that it's fine?"

He shrugs, his hands beginning to roam again, down her back and lower and—

She swats him away, lifting herself off his lap and sinking onto the couch beside him. She leans back against the cushions, has to take a few deep breaths because the shock of getting interrupted is beginning to wear off and all that arousal is still left, simmering just underneath the surface. She lets out a long breath, presses her thighs together—

"Christ, Kate."

She opens her eyes to look at him. "What?"

"You are not allowed to do that if you expect me to stop touching you."

"What? I—" She watches the way his eyes flick down to her lap, his hand following and she suddenly understands. "Oh." She forces herself to relax. "Sorry."

He lets out a ragged sigh and pulls his hand back. Thank god. She probably wouldn't have been able to control herself if he started touching her again.

"Should I go talk to her?" she asks suddenly.

"Do you want to?"

She pauses. Thinks for a second. "I-Yeah. Yeah, I do."

"Then go," he says, gesturing towards the stairs. "I'll be in the bedroom. Waiting."

She scowls at him. "Cruel man."

—

Alexis is lying on her bed when Kate knocks on the half-open door and hesitantly pokes her head inside. "Alexis?" she asks, smiling when the girl lifts her head from the book propped on her chest. "Hey. Can I come in?"

Alexis sits up. "Um. Sure. Yeah. Come in."

Kate steps inside and then stops, unsure of where to stand. "I'm, uh…I just wanted to talk to you after…that."

Alexis raises an eyebrow, looking almost amused, which actually helps. At least she's not mad. Doesn't seem to be traumatized either. "Don't worry about it, Kate."

Kate's pleased to hear her given name coming from the girl. She had to practically beg her to stop calling her Detective Beckett and she's happy to see that Alexis is sticking with it, even in this most awkward of situations.

"Are you…okay?" she asks lamely.

Alexis nods, smiling in earnest now. "I mean, it's not like I love catching my dad doing…that stuff. But you don't have to apologize or anything. It's fine. You guys are in love."

The way she says it, so matter of fact, it makes something catch in Kate's chest. It's true, but…Shit. They're doing this. They're actually doing this.

"Did he…say that?" she asks hesitantly, feeling a little foolish, a little like a seventh grader asking her best friend what her crush thinks of her, but if he actually said that to his daughter, it would—

It would make it real. He loves his daughter. More than anything in the world he loves her and he would only say that if it was true, if he wasn't planning on taking it back anytime soon.

Alexis pauses, tilting her head at Kate. "You really want to know?"

Kate has to fight against the smile that wants out. This girl's good. She knows what she's doing. It actually reminds her of something Lanie would ask her, which makes sense considering how many hours the two must spend together.

"Yeah, I do," she says honestly.

Alexis nods, accepting that. "Yeah, he said that. He's in love with you."

Kate swallows hard, feeling the truth of that settle and bloom in her chest. No wonder he's not concerned about Alexis catching them. He probably thinks it's the first of many awkward encounters to come.

Well. She hopes not. But it's a strange kind of wonderful for this to be so…okay. They're in love, the real kind, the kind where they're apart for an afternoon so when she sees him all she wants to do is kiss him, the kind where she forgets that his daughter might come downstairs and find them because all she wants is to feel him against her.

"I'm in love with him, too," she says, her voice soft.

Alexis grins. "I know."

Kate nods, smiling at the girl. "Good. Okay, well…I'll let you get back to your reading."

The girl nods. "I'll be up here for a while so if you guys are going to…"

"Yeah, don't, uh…Don't worry about that."

Alexis just shrugs and turns back to her book.

—

She finds him in the bedroom like he promised, lying on top of the covers reading. She hops onto the bed and straddles his stomach, grinning down at his surprised and happy face.

"Everything good?" he asks.

She grins, can't help it. He told his daughter. "Yup. All good."

He smiles, but his eyes narrow simultaneously in suspicion. "Why are you so…giddy?"

"Alexis told me what you told her."

"I tell Alexis a lot of things."

"True things?"

He nods, his brow furrowing in confusion. "Of course."

She flashes him another smile at that and leans down, brushing her lips along his jaw, her hands smoothing across his chest. "So," she murmurs conversationally, mouth ghosting across his. "You love me, huh?"

He stills beneath her, his eyes going a little wide. "She-she told you that I—"

She silences his stuttering with a kiss. "Already knew, Castle. Not a big secret."

"Well, yeah, but I had a plan."

"A plan?"

"Yeah, I wanted the next time I said it to be special. A romantic dinner, then a walk in the park, maybe a carriage ride—"

"Jeez, if telling me you love me is this elaborate I can't even imagine what your proposal is going to look like."

He gasps a little at that one, which was kind of her goal. He spins them on the bed, rolling on top of her so that she's tucked under his body, grinning up at him. "Kate Beckett. What has gotten into you? Since when are you so—"

"Not scared?"

His face softens immediately. He leans down and brushes a gentle kiss across her lips and then another until she parts for him, sliding her tongue against his, lazy and soft and searching. "You're not scared anymore," he murmurs into the kiss, his voice awestruck and reverent.

"I'm not," she confirms, curling her hand around the back of his neck, keeping him close. "I used to be scared. Petrified, actually. But now…"

She trails off, trying to find the words. "You were right there. You were right there all this time, just like you said, and I was fighting it, because your terrified me, but now…I just…"

"Love me?" he supplies.

She smiles. Nods. "Yes. I just love you. That's all there is. I'm in love with you."

He presses his mouth to hers again, kisses her deep and slow. "I love you, too," he whispers. Not exactly a moonlit carriage ride, but it's them, and that's even better—all he ever wanted, really. All he ever hoped for.

—

So I think I'm going to turn this into a collection of oneshots, each one about a different first for Castle and Beckett as a couple. This one would be the first time Alexis catches them. If you guys have any suggestions for more firsts, please let me know!