It was a rare day off for the both of them, the sun shining down onto New York on a crisp spring morning, still a bite in the air. The kind of day it would have been perfect to rug up and take a walk through Central Park, or head to the zoo, or one of the museums.

Until his fiancée had claimed it for very necessary wedding planning.

He added a couple of drops of vanilla to her coffee, his own mug lying steaming next to it. His mother was still sleeping away her late night last night with theatre friends, and his daughter had headed off early to the library, claiming too many assignments and too little. He'd tried to dawdle through breakfast as much as possible, but it could not be avoided any more. Castle steeled himself internally, picked up the two mugs, and headed for the living room.

It was covered in papers, Post-It notes labelling half of them (Beckett had decided to go old school- all his thoughts were either jotted down directly on his phone, or on his laptop and then synced to his phone), and she was scribbling yet another half-legible sentence on a pink square and sticking to their guest list when he entered.

"Here."

She looked up at him, accepting the coffee gratefully and breaking out into a wide smile, and a large slice of his disquiet rather quickly disappeared at that moment.

"Thanks babe." She cradled the coffee in her hands, drinking a sip while looking at another piece of paper like it was a perp in her interrogation room.

"How's everything going? What can I do?"

He settled down on the floor next to her, leaning back against the couch, and she nestled into his torso in response, her shoulder relaxing a fraction.

"Well…we're less than two months out, and there's still a ton to organise. Since your mom didn't prove to be all that helpful with the flowers, would you take care of that?"

"Done."

"OK, then there's the catering…"

They worked their way through her list steadily, generally in agreement (he was happy to go with her wishes on most of the issues), sometimes fencing over minor matters, occasionally changing plans in response to something he recalled from his previous two ceremonies, or her own experiences as a bridesmaid many times over.

His hand wandered over the small of her back, squeezing gently when she got frustrated, and the hint of cherries (still his favourite) settled around him when she lay her head on his shoulder momentarily.

Eventually, they came to the seventh item on her list. He read it out loud over her shoulder. "Bridesmaids and groomsmen."

"Yeah. We really need to sort those names out if we want them to get fitted for dresses and such."

A new Post-It appeared, and her pen hovered over it.

"How many should we have? I don't want anything too big." He proposed gently.

She nodded in agreement.

"Definitely. I was thinking three at most?"

"Three's good."

She divided the paper in two, listing their names at the top of each column.

"So, I was thinking of asking Lanie to be my maid of honour."

She peered up at him as she spoke, eyes large and green and expectant, but he was already nodding.

"I expected as much. Thick as thieves you two are. Who else?"

She shrugged in response,

"Well, Maddie for one…what about your best man?"

He pursed his lips, searching for the right words. He'd thought about this a lot in the past few days. For his first wedding, he'd dragged in his old friend Damien Westlake. Not really an option this time around as Damien was serving time for murder. For his second it had been Connolly, but he'd been the right choice for the big splashy media-worthy event Gina had made that wedding. He wasn't here.

In the end he could only come up with one choice that fit. The person who, alongside Beckett, he loved the most in his life. The person who'd suffered through his toils and tribulations and sorrows with him over the past few years. For whom he'd lay down his life in an instant.

"So, I've been thinking of an unusual best man…" He trails off, not quite sure how to broach the topic.

"It's Alexis, isn't it?" She interrupts, a warm smile dancing on her lips, her eyes bright.

"Yes. I love it when you use your mind-reading powers for good not evil."

He winks, letting out a sigh of relief he didn't even know he'd been holding in. He didn't think she'd be a total stickler for tradition, but there still had been a knot of apprehension in his stomach that was now rapidly dissipating.

"It's OK. We've never been the most traditional of couples, let's face it, and Alexis is an important member of our family. I was going to invite her to be my third bridesmaid, but I figured you might want her for a slightly more central role in the ceremony."

She stretched up, closing her eyes as she pressed her lips to his gently, and they kissed for a moment. She tasted vanilla sweet and coffee strong, of home and hearth and love, and when they both pulled apart at the same time, he rested his forehead against hers for a moment.

"Thank you." He murmured into the small space between them.

"I think it's sweet." She murmured back, eyes still closed.

They held contact for another instant, and then reluctantly she turned back to her list, pen scratching down Alexis's name on his side of the column.

"I don't think she can organise the bachelor party though." Beckett's voice tinkled with laughter as she spoke, and he grinned in acknowledgement, stroking a thumb along her ribs.

"No, I think I'd better leave something for Ryan and Sito to do, otherwise they're going to take it very badly indeed."

"As long as you don't end up in a roomful of geishas or dressed like a bad Elvis impersonator in Atlantic City."

"Well…definitely not the former. But the latter? Never say never, Beckett."

She mock-groaned in reply, but they moved on to the next item on her list. Together.

Alexis comes home later that day, while they're in the midst of cooking dinner. He's chopping the vegetables, and she's going to be in charge of the stir-fry. They're only just starting their very-well deserved first glass of red, and Beckett's much more relaxed since they ploughed through a very significant slice of the preparation. Even he feels like it is finally coming together, all the pieces falling into place.

"Hey Dad. Hey Kate."

"Hey Alexis, joining us for dinner?" His daughter already on her way upstairs after swinging by the kitchen, but she pauses to respond to his question.

"Ahh, sure. I'm going to meet a friend a bit later, but I'll be home for a while first. Where's Gram?"

"She went out to her studio for a bit, and then she's having dinner with a friend."

"Cool. Be back in a sec."

And with a couple of more bound of teenage energy, she's off.

He looks around to find Beckett smiling at him gently.

"Are you going to ask her now?"

He shrugs his shoulders in response.

"Sure. Why wait? Can we ask her together once she comes down? Because if she wants to be in your bridal party instead…" He trails of again, not really sure how to put what he wants to say into words.

Once again, his lovely fiancée rescues him.

"I'll be here for any moral support you need, and to act as back-up plan, sure. But don't worry, I think she'll jump at the chance to be your best man."

Beckett presses a kiss to his cheek, and goes back to the food preparation, and he joins her till Alexis re-appears a few minutes later, sliding onto a bar stool on the other side and watching them work.

"So, what's for dinner?"

"Stir-fry with noodles."

"Yum!"

He takes a deep breath, and under the counter, Beckett squeezes his hand.

"So Alexis, pumpkin, there was something I wanted to ask you. About the wedding."

His daughter focuses on them, standing side-by-side, blue eyes wide and bright.

"Sure, Dad. What's up?"

"Well, I know I kinda dropped the ball on telling you about our engagement, but I want-"

"We want."

"We want you to be really involved in the wedding. You've been the most important person in my life ever since you were born, and though you're an adult now, making your own way into the world, there's absolutely no one else I want standing by my side when I say my vows to Kate."

Alexis's eyes widened, glee bursting onto her face via a wide smile, and in response he could do nothing but smile too. He soldiered on to the actual question though.

"So, will you be my best man?"

She jumped off her seat and skittered around the bar, her arms opening wide into a hug. He wrapped his own arms around his sweet little girl, enfolding her into a bear hug, tears welling up unbidden into the corners of his eyes.

"Is that a yes?" He joked into her hair, spinning her around and seeing Beckett smiling at them widely herself, love pouring out of her eyes.

"Of course it's a yes, Dad! I'd love to be your best man. Woman. Person."

They let each other out of the embrace, and she turned to Beckett in turn, folding her into a hug too. Warmth poured out of his heart and throughout the rest of him when he saw the genuine affection between them, the two most important people in his life.

The hugs concluded, Alexis burbled at them both, her happiness evident in the grin that seemed permanent on her features.

"It's gonna be great, what are my duties?" She flicked a glance across at him. "I assume I can delegate the drinking and debauchery to someone else?"

"Oh yeah, that's definitely not going to involve you."

Beckett rolled her eyes and snuck a smile in at the same time, before pointing him back at the vegetables.

"You, go and chop. Well, Alexis, we're still figuring out exactly how long the ceremony is going to be and what it's going to involve, but we definitely want you to do one of the readings…"

He chopped happily as the wedding planning continued, Alexis pitching an idea or two of her own. He was happy, because the only thing he'd really wanted was now in place.

She might be the most unusual best man in the world, but for him, for them, for this wedding, she was the perfect one. And that's all that mattered.

A/N: So ever since the wedding arrangements began, I really wanted Alexis to be Castle's best man. It fit their closeness and the importance of their relationship in his life (and hence in Beckett's), and I never really saw C/B being all the concerned about being traditional or adhering to convention when it didn't really suit them. Once that became canon in L&B (making me very happy), I really wanted to explore how that might have happened before the ep began, how Castle and Beckett would've approached it together (because it was done with Beckett's full approval and support). Anyway, let me know what you thought about this little ficlet, I always really appreciate getting feedback on my writing. Thanks!