"It has to be a boy."
She looks across at him from her uncomfortable position on the exam table, unable to suppress a smile at just how serious he looks.
"Alexis cannot be the one to correctly guess the sex of our baby," he reiterates, holding out his phone to show her a teasing message from Alexis inquiring about her baby sister.
"Odds are fifty-fifty, Castle," she reminds him, and he huffs, rolling his eyes as if fifty-fifty isn't good enough for him.
"Why is she so adamant it's a girl?" He wonders, and Kate smiles, entertained by just how much this little wager is getting to him.
It wasn't supposed to be so serious. She merely asked Alexis whether she thought the baby would be a boy or a girl, knowing that she and Castle both had strong suspicions it would be the former.
But when Alexis responded confidently that it was a girl, it all got a little out of control.
Castle proposed a friendly wager, one he apparently now regrets.
She's just thankful Alexis is so excited to have a sibling.
She's well aware that most twenty-two year olds would be considerably less enthusiastic about the prospect of their father having a child with his third wife, but Alexis has been supportive from day one.
When they'd specifically planned a family dinner, sharing the news over pasta and sparkling water, Alexis had grinned, congratulating them enthusiastically before starting in on questions about the pregnancy and potential names for the baby.
Even after making an effort to forge a close relationship with her stepdaughter, Kate found herself staggered by Alexis' reaction. She'd been wary of sharing the news; concerned that Alexis would feel they were replacing her, that they wouldn't have room for her in their family with the new addition.
Kate had been hoping for mere acceptance of the news.
She hadn't expected excitement or joy or anything more than a neutral reaction.
She hadn't expected Alexis to take her shopping for maternity clothes, knowing that while Castle was all about shopping for the baby, he was less aware of the need to shop for her.
She hadn't expected her to drop by the loft every few weeks with something she just had to buy for her baby sister.
Every day she finds herself amazed by the daughter Castle raised largely on his own, and she feels immensely lucky to have the young woman as a stepdaughter.
If their child ends up half as impressive as Alexis Castle, she'll be a proud mother.
She already is, and for that reason, she's happy for Alexis to win this little wager.
By the look on her husband's face though, he is not.
"It's a matter of pride, Beckett," he says defensively, recognising the teasing look on her face. "That, and the consequences. Relinquishing the rights to our first child's middle name⦠What was I thinking? I mean, really, what if we have a daughter with a perfectly ordinary name?" He whines, and she can tell he's playing it up for her amusement.
She gives him a smile, reaching for his hand and ignoring the opening for more teasing, instead going for gravity.
"I'd be thrilled," she says, brushing her thumb against his wrist.
He smiles at her, pressing a kiss to her lips.
"I would, too," he agrees, letting the moment fade organically before he mutters.
"I'm still hoping for a boy."
If the doctor is aware of the amplified anticipation level in the room, she doesn't let on.
Castle is squeezing her hand tightly as they see their baby on the monitor, and she's so overwhelmed by the image that she almost forgets the reason for the appointment.
"Looks like you're having a girl. Congratulations," Dr Allen says, smiling, and she beams, struck by the tangible proof right before her eyes that she is going to have a daughter.
"Oh, wow, Castle."
She looks over to her husband to confirm that she's not the only one in awe, and she sees his eyes mist over.
"A girl," he smiles, captivated by the image, and she nods wildly, turning back to the screen.
They're going to have a daughter.
They don't even contemplate the ramifications of the news until they open the door to the loft and find Alexis waiting, impatient.
"Well?" She demands, her curiosity evident, and Kate cracks first, beaming at her.
"It's a girl," she confirms, and Alexis rushes to her, hugging her tightly.
"A girl. I knew it," she says, grinning. "Ha. I knew I was getting a sister."
Castle looks defeated, or is at least playing the part, until Alexis continues.
"For the name I'm thinking something classic. Common. I already have a list."
Her eyes glitter teasingly, and Castle moans.
"You sure you want another one of these, Kate?" He asks, jokingly, but Kate just wraps her arm around Alexis' shoulders.
"Sounds good to me."
