A/N: Thank you again for the mass of comments to this story. They are very much appreciated.

Rating change for this final chapter.

Chapter 3 – Kate

Previously…

Castle is lying on the sofa, his feet propped up on a pile of cushions, the TV remote held aloft in one hand, a bowl of popcorn balanced on his stomach.

"Hey! I'm home," calls out Kate, giving Castle a brilliant smile, as she drops her keys into the bowl by the front door. "And there's someone here who wants to see you," she adds, holding out her hand to Alexis, who's lingering out of sight behind the open door.

"Lanie's here?" asks Castle, his excitement at the prospect of seeing their friend ringing clear as a bell in his voice.

He struggles to a sitting position, sending whisper-light pieces of popcorn dancing and jumping out of the bowl that was resting peacefully on his stomach until a second ago.

"No. Better than Lanie," grins Kate, her long fingers wrapping around Alexis' wrist to draw her out from her hiding place behind the front door.

"You had dinner with Maddie?" squeaks Castle, dumping the bowl on the coffee table and swinging his feet to the floor.

That he runs his hands through his hair and smoothes down his sweater isn't lost on Kate. She always knew that Castle was impressed by her girlfriend, Madison Queller: the successful, attractive restaurateur. Seems he still is.

"Did you tell her we're going to have little Castle babies?" he calls out giddily, before Kate has a chance to correct him and tell him exactly who she has brought home with her tonight.

She feels Alexis yank her hand out of her grasp and then address her in a small, almost wounded voice.

"You're pregnant?" she whispers, taking a step away from Kate, backwards into the hallway, her eyes radiating a look of deep hurt and betrayal.

Kate glares at Castle for a split second - who now looks thoroughly confused - and then she spins around to deal with the more urgent issue of his daughter.

"Is that Alexis? Is Alexis here?" Kate hears him asking, his own voice suddenly flattened by concern, the ringing tone of excitement now gone.

"Alexis," says Kate, ignoring Castle for the moment, as she attempts to firefight one issue at a time. "Alexis, look at me," she asks, reaching for her arm.

"Don't," says Alexis, backing further away, though Kate is relieved to see that she isn't fleeing for the open doors of the elevator at least.

"Alexis, I'm not pregnant," Kate reassures her. "I meant what I said at your apartment. When we set a date for the wedding, you'll be the first to know. And when…if there is a baby…the same thing. No one is keeping anything from you."

"Then what is my dad talking about?" she asks, her eyes wide and confused.

"It's an old joke my friend Maddie made once…years ago. She didn't think your dad could hear us talking and she embarrassed me. That's all."

"So it's just a joke?"

"For now, yes," says Kate, not wanting to lie to the girl. "We've just starting talking about these things."

"So you have talked about it?"

"A little. Would that be a problem?"

"I never thought I'd have a brother or sister," confides Alexis, her expression softening now that she feels included, since Kate has been thoughtful enough to ask her opinion.

"Do you want one?"

"I—yeah," the girl nods, giving Kate a tentative smile.

"Good. That's good," replies Kate, with some relief. "But you know even if we are lucky enough to have a baby, you'll still be your dad's number one priority. Having a little brother or sister won't change your relationship with him. In the same way my joining your family hasn't changed anything. Now, please come inside and talk to him. He's probably hiding out in his office, mortified," laughs Kate, taking Alexis by the arm. "And remember what I said. He loves you more than anything. You can work this out," whispers Kate.

When the two women enter the loft arm-in-arm, they are both surprised to discover that Castle has in fact been standing just inside the front door, pacing anxiously. If the look of utter gratitude and devotion he gives Kate is anything to go by, he's heard every word of their last exchange.

"Alexis and I went out for dinner and we had a long talk," says Kate, confidently. "She wanted to see you," Kate tells Castle, feeling Alexis' posture stiffen beside her as soon as these words are out.

Castle switches his gaze from his fiancé's face to that of his daughter, who is standing frozen and pale, her lips a bright Snow White red, her fine brow lowered a little in what could easily be described as a scowl.

He can't hold his daughter's gaze for long, so he switches back to Kate's more sympathetic face to find her still talking.

"So…I'm just going to go change. I'll leave you two alone to talk," she says.

Alexis nods slightly at Kate as the Detective releases her arm and squeezes her hand in a final act of support, before making a move to cross the loft and head for the bedroom.

"No, wait!" exclaims Castle, trailing after Kate.

Alexis watches him go, and then she wanders over to the sofa and sits down heavily, emitting a long sigh.

"Can I talk to you for a second?" asks Castle, attempting to follow Kate into the bedroom.

"Castle, your daughter is waiting. Go! Talk to her," she tells him, smiling encouragement. "In fact, you know what? Don't talk. Listen first and then talk," she advises her fiancé.

"Can I at least say thank you?" he asks, squeezing through the gap in the bedroom doorway Kate has left open, while she keeps the room closed off with her foot.

"Thank me once you've sorted everything out," she suggests, patting him on the chest.

"Hey," Castle quietly tells her, stepping in closer, tugging on the front of her coat.

Before she can gather herself he's gently cupping both sides of her face in his hands and leaning in to kiss her forehead.

Kate's hands rise automatically to settle on his waist, bunching a fistful of black cashmere in each. She just can't help herself anymore when he gets so near and is this tender with her. She finds her eyes drifting closed when his lips press softly against her skin, his nose nuzzles her cheek for a brief second, and then he relocates to find the corner of her mouth with his own.

"You're going to make an amazing mother," he whispers in her ear, withdrawing before she can scold him that this isn't the time for sentimental talk like that.

"Rick," she murmurs, swaying drunkenly at his light, intoxicating touch, "just go out there and talk to the child you have. I think she's ready to hear what you have to say. But promise you'll keep an open mind. Meet her halfway, okay?" suggests Kate, letting her fingers trail down his chest, before she forces herself to let go completely.

Castle nods silently, his eyes softened to deep smudges of Prussian blue by the love she can see unmistakably swimming there just for her.

"I love you too," she assures him, in response to his own unspoken declaration, letting her fingertips glance off his cheek, before she pushes him away with a gentle finality and closes the bedroom door.

Out in the living room, Alexis is rapidly thumbing her way through a copy of Forensic Science Magazine that she found lying on the coffee table. Castle watches her pause over an article entitled: 'Texas Execution Withdrawn Due To New Forensic Law', her porcelain-smooth brow crinkling into a frown as she reads intently.

"Find something interesting?" he asks her, hovering a couple of feet away until he gets a signal that it's okay to sit down.

It may be his home, but the redheads in his life rule the roost around here when it comes to a lot things he has learned to his cost over the years.

"Just something that might help with an Innocence Review case I'm working on," replies Alexis, vaguely, still absorbed in reading the article.

"I think you skipped past the article on Halloween Monster DNA. That was my personal favorite," Castle rambles on, nervously.

"Of course it was," says Alexis, a little coolly, before setting the open magazine down on the coffee table and glancing up to give him the barest of smiles.

"Alexis, can we talk?" asks Castle, seeing his opening, this tiny chink of light, and chasing after it.

When Alexis nods in agreement, he finally sits down on the sofa, staying far enough away that he isn't crowding her.

"Would you mind if I go first?" asks Alexis, surprising him, after the sullenness he experienced outside her apartment the night before.

"Uh…yeah, sure. Of course," he replies, pressing his hands between his knees and sitting up straight to hear what she has to say.

"When you came to my apartment, I was maybe a little…actually, scratch that. I was rude to you last night, dad, and I'm sorry."

Castle watches her apologize in grateful silence and he vows to do something incredibly special for Kate the second he gets a chance, because he recognizes her cool, fair, skillful, diplomatic hand all over this.

"I shouldn't have kept you standing out in the hallway and I apologize for questioning your relationship with Kate. That isn't my place and…Kate is great. I know you make each other happy. She's good for you, dad."

"Thank you. I appreciate you telling me that. Apology accepted."

"That doesn't mean I don't think you were wrong to judge Pi without getting to know him first," she adds, a little tartly.

"I know. I wasn't very welcoming. I am sorry. Maybe a little notice next time?" he suggests, gently, tilting his head to catch Alexis' eye.

"Dad, there won't be a next time," Alexis points out, trying to rein in her frustration with him for still wanting to spirit them back in time to her childhood. "We have our own place now. So you don't have to worry about us getting under your feet or…or invading your private time with Beckett."

"Alexis, you know that there will always be a place for you here? This is your home, and no matter how old you get that will never change," Castle assures her.

"I know," she says lightly. "But it's time for me to make a home of my own."

"Honey, you seem in such a rush to grow up and move on," Castle laments, his features failing to mask his disappointment. "You know you don't have to…I love having you here. We both do. The engagement doesn't alter that."

"I know you think that, dad, but actually it does. And you have my full blessing…you do. I promise," she says, nodding when he looks at her in surprise. "Kate and I talked. She made me see that this is more about me growing up and our family changing. But it's all good change. I don't think you could have found anyone better than Kate. She makes our whole family better. And who knows, maybe I'll have a little brother or sister to fuss over before long," Alexis adds, with an impish grin.

Castle suddenly has a lump in his throat, stunned that they have arrived at a day where Kate Beckett - tough, snarky, independent, closed-off Kate Beckett - has blossomed into this open, caring, wonderful woman who is becoming the glue that binds his own little family together.

"Alexis, that's very generous of you," he manages to squeeze out around his tightening vocal chords. "And I'm sorry I haven't been so charitable towards Pi."

"I know that you're worried about me, dad. But I'm trying to make good choices. You need to trust me more. I've always worked hard and I really want to make something of my life. That hasn't changed because I'm with Pi."

"I'm glad to hear that," says Castle.

Though deep inside he knows his idealistic daughter's words are well intentioned, he is prepared, as her father, to be there to pick up the pieces if all doesn't work out as well as Alexis hopes. And he's equally confident after today that he will also have Kate by his side to step in, wipe away tears and provide a shoulder to cry on if necessary, and that is a massive comfort to him; having someone so strong to shoulder the parental burden with from now on.

"I know he's maybe a little…different. But, dad, he's a good person," Alexis insists. "You just need to spend some time with him…get to know him," she says, enthusiastically, her cheeks flushed pink and eyes suffused with love, as she talks about this young man Castle can't ever imagine embracing wholeheartedly.

But he knows that he must try for the sake of his relationship with his daughter. Such is a father's lot.

"And I promise I'll give him a chance from now on," he says, thinking, 'fake it til you make it, Rick'.

"Thank you. That's all I'm asking," replies Alexis, folding her hands neatly in her lap in a way that reminds Castle so much of his child at five - prim, proper and precious for her age.

"Good, because I hate it when we fight," admits Castle, giving Alexis a tentative smile.

"Me too," she agrees, her own shy smile matching her father's. "Truce?" she asks, extending her hand for him to shake.

"Truce," nods Castle, pretending to shake her hand.

He pulls her into a bear hug that is more of a tackle, spilling them across the couch. Eventually they manage to untangle themselves, laughing and a little out of breath, the earlier tension dissipated now that they've had a chance to clear the air.

"How about you bring Pi over for dinner Friday night? I'll make a huge fruit salad," Castle teases, giving Alexis a wink.

"He eats vegetables too, dad," scolds Alexis, adding, "and nuts and seeds," as if this will makes a huge difference to how her father views her offbeat boyfriend.

Kate is leaning on the doorframe just inside the shadow of protection afforded by the bedroom, watching them converse. She feels a sense of pride at the small part she played in helping achieve the rapprochement they've gained with Alexis today.

She lost her own family at this exact age and hasn't felt fully part of one since. Today she feels as if she might be regaining that sense of family that she lost, even starting to make a family of her own. She also feels as if she's growing up just a little bit more too, though that might seem ridiculous to some given her age, life experience and the serious nature of the job she does. But living as part of a family and having to take children into consideration requires you to behave in a more selfless, mature manner than being single ever does, regardless of age. Kate recognizes that for the first time tonight, and she likes how these new bonds they're forging and the weight of that responsibility feels on her shoulders. They're not binding in an unpleasant way, or the burden she might once have thought they would be. She feels warm and secure and proud watching her fiancé hug his daughter and be able to laugh with her again.

"I have a great vegetarian recipe for Pumpkin-Acorn Squash soup," suggests Kate, suddenly appearing out of the shadows and crossing the living room to join them. "Served with toasted pumpkin seeds on top," she tells Alexis, raising her eyebrows and getting richly rewarded for her help with a smile.

"Sounds delicious and perfectly seasonal," the girl nods. "I'm sure Pi will love it. Could we make it together?" asks Alexis. "I'd like to learn."

"Sure," smiles Kate, sitting down on the arm of the sofa close to Castle and resting a hand on his shoulder.

"So, we're on for Friday? Assuming the bees cooperate, line up for role call and Pi doesn't lose count and have to start over," Castle teases.

"Dad!" "Rick!" exclaim the women in unison, both appalled at his joke.

"Too soon?" he asks, yelping when Kate picks up a handful of popcorn and throws it at Castle's head, totally surprising him.

Alexis can stop herself from laughing at the look of utter shock on his face.

"Sorry, sorry, I couldn't resist," he says, holding up his hands when both women glare at him, threatening to arm themselves with more popped kernels. "I promise I will bee on my best behavior," he adds, fleeing to the kitchen to get them all a drink when Kate threatens to ban him from the precinct.

"That seemed to go pretty well," Kate comments to Alexis, once Castle is out of earshot. "I'm really proud of you. You did a good thing tonight."

"Thank you," says Alexis, graciously accepting the compliment, before reaching out to give Kate a hug. "But I think you deserve most of the credit. I'm sorry I behaved like a brat before."

"Hey. We're moving on, remember?" says Kate, patting her knee. "All forgotten."

Later, when they're lying in bed, Kate's warm, naked back tucked up against Castle's bare chest, their bodies flushed and stuck together, he kisses the shell of her ear and whispers into her hair.

"You were amazing today. Thank you for going to see her and talking her round."

"I'm just trying to see both sides here, Castle," she assures him, leaning back into the warmth and solidity of his body and drawing his arms more tightly around her. "I hate to see you two fighting and you so unhappy."

"She said you make a great addition to this family. My little girl said that…about you!" he gloats, so pleased at the way things seem to be working out.

"You realize she thought I was pregnant when you threw out that stupid Maddie line about 'little Castle babies,'" she tells him, making air quotes in the candlelit bedroom and then nudging him in the ribs.

"I know. I'm sorry. Me and my big mouth. But I wasn't to know that the mysterious 'friend' you'd taken to dinner was actually your step-daughter-to-be, Mrs. C to Be," teases Castle, tickling her.

"Shhh, enough," giggles Kate, her whole body shaking. "I'm getting Pi flashbacks. Just the man, the mustache and that towel," she confesses, wrinkling her nose.

"Not sure I like where this is going."

"Eww! Castle, no!" Kate protests, swatting his arm when he starts laughing at her.

"I know the Maddie faux pas was partly my fault," Kate admits, once they both sober up. "But I wanted to surprise you."

"And you did," he admits, sweeping her hair off to one side and then gently kissing his way down her damp neck, all the way to the elegant dip in her collarbone. "You constantly surprise me, Kate Beckett."

"Good. I like to keep you on your toes."

"On my toes, on my knees, on my back, in my bed," he whispers, with a smile, sending puffs of cool air over her flushed skin.

Kate slowly starts to move against him when he begins to roam the smooth, curvaceous outline of her body with his large hands beneath the silky, cotton sheets. She feels her skin flush and tingle at his familiar touch, her whole body coming alive in response to the dizzying sensation of Castle's slow, sensual love-making.

"You know...Alexis seemed quite open to the idea of having a baby brother or sister," admits Kate, tentatively, biting her lip.

"So...are we practicing yet?" he asks, cupping her breasts, their soft weight so erotic against his palms, nipples stiff and insistent when he circles them with the pad of his thumb.

"Are you asking what I think you're asking?" rasps Kate, a little breathlessly, her fluid, languid, continuous movement against his body driving him insane.

"Did you just answer my question with a question, Beckett?" teases Castle, holding her tightly by the hips and starting to move with her.

"Did you?" giggles Kate, when he forces his knee between her thighs and then rolls them both onto their backs so that she's lying on top of him, her back to his front, her legs spread wide across his well-muscled legs.

She gasps and he grunts when he touches her intimately, her body still sensitized and slick from their first frantic encounter tonight, when Castle's need to display his gratitude rapidly spilled over from the living room into the bedroom, immediately after Alexis left.

"Do you want to set a date first? Or do we throw away those pills and get on with adding to our family?" he asks, smoothing one hand over her flat stomach to keep her pressed tightly against him, while he strokes her towards shivering, writhing ecstasy with the other hand.

Kate turns her head feverishly to one side, kisses him passionately on the lips, arching against his hips as he drives her higher; her breasts thrust out magnificently, tender nipples peaked sharply with desire in the cool air of the bedroom, as she pants for breath.

"If there's a law that says we can't do both," she whispers, licking her own kiss-bruised lips in anticipation, "I'm not aware of it."

"You mean that?" asks Castle, excitement immediately filling his voice.

"Let's flush the pills," she nods, squealing adorably when he rolls them onto their sides and turns her so she's facing him.

"And if I knock you up before we make it down the aisle, promise you won't be mad?" he asks, stroking her cheekbone with his thumb as he stares into her twinkling, smiling eyes, so close that she fuzzes in and out of focus.

Kate laughs, kissing him impulsively, her arms snaking up round his neck to hold him tightly against her.

"I know your little swimmers are probably Olympic standard, Castle. But I'm pretty sure even we can manage to get married before I start to show."

"God, I can't wait to do this with you," Castle declares, enthusiastically, lowering her onto her back, his body stretched out above hers, eyes radiating so much love.

"Don't tell me, Castle. Show me," she whispers, arching up to steal another deep, passionate kiss from his soft, eager mouth.

She threads her fingers through his hair as she cradles his head against her breast for one long, tender moment, watching him listen to the strong, reassuring beat of her heart, before she releases him - this amazing, generous man who is now her family.

"Let's make a baby," she smiles, tears of joy swimming in her eyes.

Thoughts?