A short one-shot I came up with based on this statement: "I don't need a stupid app to tell me that our kids will be cute." Set early during their engagement.

Disclaimer: I do not own Castle.

It was a slow day, no murders just paperwork. Kate was at her desk focusing on the stack in front of her, or at least trying to. She wanted to finish it early so her and Castle wouldn't have to stay any longer than necessary. But it was hard to stay focused when every 10 seconds there was the click of the camera followed by a loud laugh and grumbling.

It started this morning when Castle chose to come into work with her even without an active case, insisting that he would keep her company. However, after about an hour or so he discovered a new app on his iPhone. It allowed you to take pictures of 2 people's faces and it would merge them together to create a picture of what their child would look like.

Castle began with his face and other celebrities faces, until Espo and Ryan came over to inquire what he was up to. The three of them then started with each other's faces. Currently they, well really just Castle, was laughing at the mix of Ryan and Espo's face which turned out to look like a hispanic elf. Castle had tears running down his face while the two detectives just glared at him.

"Kate! Look at what Espo and Ryan's future child will look like! It's like a character straight out of Lord of the Rings!"

"Not now Castle, I'm busy." Kate replied, not even looking up from the work on her desk.

"Oh c'mon, take a break. Hey! Let's use our faces." Castle said as he made his way toward her, camera ready to capture her face.

"No, thanks." Kate replied bluntly.

"Please?! It'll be fun!" Castle begged.

"No, it's pointless."

"Why do you say that?" Castle questioned.

"Because I don't need a stupid app to tell me that our kids will be cute. I already know they will."

There was a pause.

"You want kids?!" Castle squeaked

After a beat, the pen Kate was holding clattered to her desk. She looked up at him like a deer caught in headlights. Her mouth open and closed like a fish, trying to come up with some sort of explanation. When she came up with nothing, she stood from her chair abruptly.

"I need coffee." She said before she all but ran into the break room.

She was standing in front of the expresso maker, her hands resting on the counter with her head held down. She didn't even notice the door open and close until Castle spoke up.

"Kate?" He said quietly, as if not to startle her.

Silence. She said nothing. Instead she tried working the machine which wasn't turning out too well since her mind was not focused on the task.

Castle came up behind her. Hands resting on either side of hers and his mouth near her ear. He pressed a soft kiss there before he spoke.

"A little boy with curly brown hair, bright blue eyes, all while adorning a mischievous smile. And a little girl, brown waves cascading down her back with emerald green eyes and just as stubborn as her mother."

"What?" Kate asked, clearly confused.

"Our kids." He replied simply. "I think about it too. Quite often in fact."

"Yeah?" She whispered, like it was a secret, turning her head to meet his gaze.

He smiled at her, his eyes crinkling at the corners. "Always. I just didn't know if you wanted kids, or if it was too soon to have the conversation."

"Well I didn't know if I wanted them before. But ever since we got together it's been on my mind more often than not. I even started having dreams."

"Yeah?" Castle asked as he looked at her in awe. "What happened in the dreams?"

"Sometimes it's of you and our son trying to deny whatever mischief you got up to that day. Or of you pushing our daughter on the swing, her high pitched screams and your deep laughter echoing through my ears." Kate said looking off into the distance as if she were replaying the scenarios in her head.

After a beat, she spoke again. "I want it one day."

"One day, Kate. One day." He replied as he wrapped his arms around her waist.

"Soon, Castle. One day soon." She said and leaned into to press a kiss to his lips.

"Plus, if we wait too long, we'll have to worry about you breaking a hip while playing with the kids." She added, eyes sparkling with mischief as a playful smirk took over her mouth.

Castle gasped with mock indignation written all over his face. "I'll have you know, Mrs. Soon-to-be Castle, that I am very young. And I'll show you just how young I can be later tonight." He promised as he hauled her back against the solid frame of his body.

Kate gasped and grabbed his forearms in response.

Castle smiled at her reaction and kissed her neck. "You're right, you know?"

"Right about what?" Kate asked as she closed her eyes at the sensation of his lips against her neck.

"Our kids. They'll be damn cute."