A/N: Happy holidays, guys! I know I've been MIA for a long time, but I got inspired a few days ago, and even though this will probably be finished by the end of the Christmas holidays, I wanted to post it anyway. Always late... Meh.

This could be labeled as some kind of sequel to my story "An Unexpected Little Surprise", which was finished a couple of years ago, but I think anybody could read it if they know these few things:

*On my previous story Castle found out he had a secret child with a one night stand who gets murdered.

*After taking paternity tests and going through all the procedures he got the custody of the boy.

*The kid is super attached to Kate since the beginning.

I think that should help the ones who haven't read the first part to understand what's going on on this one. I hope you guys enjoy it.

Please, let me know what you think.

Chapter 1

The sun picked through the half-open blinds, tickling Kate's nose and making her eyes flutter. If only she could stay in bed and skip work for just one day. She kept finding herself wishing that same thing more and more often lately. Maybe the season had something to do with it. Christmas was not exactly her favorite time of the year. Even now, that she had a family to celebrate it with, it still made her feel all melancholic and blue.

She turned around in bed, stretching her limbs as far as she could and expecting to find her sleeping fiancé snoring softly by her side, but when she opened her eyes, she was faced instead with a set of tiny feet stuffed into fluffy Rudolf the Reindeer socks that were almost coming off from twisting and turning all night long.

Kate sighed and ran a hand along one of the chubby, little legs that were coming out from underneath the comforter. It was the third time Aidan joined them in bed that week.

Normally, when that happened, one or both of them would notice the kid coming into the bedroom, and after comforting him or even letting him fall back asleep on their bed, Castle - most times, since Kate would fall asleep with Aidan curled at her side - would pick him up and take him back to his own bed. But lately, the little rascal had developed ninja skills and none of them was able to notice when he entered the room or even got into bed with them, just finding out they had a little visitor once they woke up in the morning.

She smiled softly at the view her two boys made. Castle sprawled face down on his side of the bed, both arms framing his head on the pillow, his hair sleep-tousled and spiking in every possible direction. Aidan right in between the writer and her, laying upside down, his body hidden under the covers, with just his socked, little feet peeping out.

Turning the covers down, she fished Aidan from underneath them and flipped him, placing him on her side of the bed and covering him with the comforter again. It was a real blessing that he had his father's ability to sleep like a rock and be dead to the world once he fell under Morpheus spell.

With a last longing glance towards the bed, she picked her clothes for the day and padded her way to the bathroom stifling a yawn.

When she came out of the en-suit, all clean and ready to roll, Aidan was already awake and waiting for her patiently, sitting crossed legged on her side of the bed, his hands playing absentmindedly with a loose thread on the sheets.

The boy's face lit up when he saw her and he smiled a huge toothy grin before crawling his way to the end of the bed, jumping down easily and taking the hand she was offering him to lead him to the kitchen.

Kate helped him climb on a stool and placed a kiss to the top of his head, ruffling his already too long hair. They really needed to take him to get a haircut, and soon.

She opened the fridge and took out a bowl with fresh fruit and placed it on the kitchen island, right at Aidan's reach, so the boy could eat some while she worked on their breakfast.

After getting the coffee maker started and putting some toast in the toaster, she turned around, a raised eyebrow and a smirk on her face, causing the kid to stop chewing on the strawberry he was eating and smile at her sheepishly, full mouth and all.

"So. What happened last night, munchkin?" She asked amused. "Was it monsters under your bed or aliens from outer space knocking on your window?"

Aidan chuckled at that and squinted in thought. "Um… I think it was the aliens." He said with a very serious expression. "They're scary."

"Oh, I bet." Kate replied, picking up two pieces of toast and putting them on a plate that she served to Aidan with a glass of chocolate milk. "But if you were so scared, how is it that you didn't wake us up? Daddy could have gone to your bedroom and scare the aliens away, you know."

The boy frowned and shook his head, giving her an outraged look. "No, Katie! Daddy's powers don't work with aliens."

"Oh, I see. And what about mine? Would mine have worked on them?" She asked amused, knowing that Aidan pretty much thought she was some kind of superhero.

"Uh uh." The boy replied, a piece of toast in his mouth and a chocolate milk moustache adorning his upper lip. "They are not afraid of cops. They have laser guns, Katie. Those are worse than bullets. They can disintegrate you." He explained solemnly. "Don't you remember 'Mars Attacks'?"

Kate's eyebrows raised in surprise at that. "When in the world have you watched 'Mars Attacks'? That is not a children's movie, bug."

Aidan shrugged and scrunched his nose in an adorable way that reminded Kate of the boy's father, knowing he had just given away some secret information. "I watched with daddy a few weeks ago. He said it was fun, but it was scary." He mumbled against the rim of his glass. "Do you think aliens are gonna come and kill us all?"

His eyes were big and uncertain and Kate's heart hurt a little at the little boy's trepidation. The poor thing… She would have to have a long talk with her fiancé about what was appropriate to let an impressionable almost 5 year old watch and what was not.

She reached for Aidan's hand and squeezed it in her own, moving closer to him over the kitchen island. "No, baby. I am sure we're safe." She reassured him. "What you watched with your daddy was just a movie. It was not real, you know that, right?"

"Uh huh."

"Ok, then."

She cleared up the breakfast bar and picked the boy up in her arms, hugging him hard. "If you get scared at night you have to wake us up, ok, bug? If you don't do it we can't know that you're scared and won't be able to help you."

"Okay." He breathed against her neck. "I'm sorry."

"No need to be, sweetie." She said, pressing a soft kiss to the boy's forehead. "Now let's go wake up your old man. You guys should be getting ready for your last day of pre-school of the year."

It was around 2:30 pm when Castle arrived at the door of Miller Preschool to pick up Aidan, after a long and productive morning.

After leaving his son at school, he had been able to finish three chapters of the new Nikki Heat novel and even had time to go grocery shopping, saving Beckett the inconvenience of having to go with them after work. Shopping with two grabby hands coming out of the cart, trying to pick up all the stuff in the candy isle was not exactly easy and it drove his fiancée a little insane.

He waited for a few minutes, sharing tight smiles and nods with other parents, until the doors opened and a couple of lines of children preceded by their teachers came out of the building; the kids giggling and screaming, happy to be going home to their families and start the so awaited Christmas break.

Short seconds later he was hit by a tiny body who attached to his leg and looked up at him with his same blue eyes.

"Hi daddy! I missed you." The boy chirped. "Are we picking Katie up at the precinct?"

Castle laughed and crouched to be at the boy's height, ruffling his hair and softly pinching his cheek. "Yeah, buddy. We are. But first we're going to have some fun at the park, ok? And I missed you too, by the way." Aidan gave him a huge smile and stepped closer to hug him tight, which gave Rick the chance to pick him up and put him on his shoulders. "Hold tight, champ, we have a long walk ahead."

They arrived at the precinct by 4:30. It was a little early, but he knew when Kate saw they were there, she would try to get them out as soon as possible. She didn't like the idea of Aidan being surrounded by criminals and crime scene pictures hanging off the murder boards.

Whenever he stepped into the bullpen with the kid, Kate gave him a reproving look and they had the same talk once they got home about how he used this as a tactic to make her leave earlier.

He secretly thought that having her home early, even if it was by just 10 minutes, was worth suffering the "Beckett wrath".

As soon as they came out of the elevator the boy spotted Ryan, who was at his desk talking on the phone, and ran to him calling "Uncle Ry! School is over!"

The cop hung up the phone and looked up surprised by the kid's pitched voice smiling widely when he saw him running towards his desk.

"Hey, bud! That is awesome!" He replied to the cheery boy. Then looked up at Castle and shook his head at him, a somber grin pulling his lips upwards. "Beckett is gonna kill you, man."

Castle shrugged and gave his friend an unconcerned smirk. "Where is she, by the way?"

Esposito came out of the conference room carrying a big brown box with him and placed it on his desk. "She disappeared a while ago into the break room. She was on the phone with someone." The detective informed him, before high fiving Aidan and going back to his job.

"Ok, bug. Why don't you go find, Kate, huh? The sooner she knows we're here, the sooner we'll be going home."

She had been waiting for Lanie's call for about two days, when she visited her friend to ask her a huge favor, but right now, listening to what the ME was telling her, she would have rather not heard from her at all.

"I can't be pregnant, Lanie. Are you absolutely, 100% sure?" She questioned her friend for the thousandth time, her voice quivering.

Lanie sighed. "Yes, Kate. I am 100% sure. I did a blood test, remember? Three times. No chance for a mistake. You and writer boy are having a baby."

"Shit!" Kate mumbled, rubbing her forehead insistently, trying to come to terms with the new developments in her life. "This is… This is not good."

"Why? Kate, I know you're planning your wedding, but you already have a kid. What would be so wrong about having another? You told me you wanted to have kids with Castle not long ago." Lanie was trying to be the voice of reason here, but her friend was freaking out so much, that it was becoming an impossible mission.

"And I do. I want to have a baby with him, but this is not the best time… Aidan… He's not even 5 yet and he's so needy, Lanie. I can't divide my time between two kids. Hell, I can barely divide my time between work and home. How am I going to do this?"

The ME snapped her tongue and let out a deep breath. "The same way you did it when that boy burst into your lives over a year ago. You just do it, Kate." She reminded her. "You are a wonderful mom for that kid, and you will be a wonderful mom for this one. Stop second guessing yourself."

Kate groaned. "This is not the same, Lanie. Aidan was already three when we got him. I… I've never been responsible of a baby for more than an evening when I was a teen. To be honest, 3 am feedings and diaper changes don't sound very appealing right now."

"Neither does sharing your bed with a four years old, or staying up with him until the wee hours in the morning because he's having nightmares, but you do it, Kate. And you don't mind one bit because you love that kid." Lanie offered, trying to make her friend see that she was going crazy about nothing.

Kate sighed loudly and ran her fingers through her already tousled hair. "I know. It's just… Do you think it will be different? I mean, this child being Castle's and mine… Should I worry about Aidan? He's so attached to me, and he keeps worrying about me not being his mom. It's like he expects me to walk away someday and if we have a new baby in the house… I don't think he is ready for that and the last thing I need right now is having to deal with a jealous kid."

Aidan listened to Kate from his hiding place behind the door. He had been waiting for her to come out so he could scare her like he did at home all the time, but after listening to her talking on the phone, he felt his little heart sink.

She didn't want to deal with a jealous kid, and he was that kid.

His daddy and Katie were going to have a new baby. He had no idea how that worked, but apparently, parents didn't have much of a say about when they had their babies, and that meant he was becoming a nuisance; at least to his father's fiancée.

The tears started forming in his bright blue eyes, but he kept them at bay. He had to come out to the bullpen again, and he didn't want his dad to know what happened.

When he came out Castle was waiting for him sitting on his chair that still remained unmoved beside Beckett's desk, even though he didn't get to sit on it very often anymore.

"Hey, buddy. Did you find Kate?" Castle asked, brows furrowing at the kid's pouty face.

The boy just nodded and ran to Ryan, who was talking on the phone again, but picked him up and sat him on his lap, ruffling his hair.

Not two minutes later, Kate came out of the break room to find her two boys waiting for her in the bullpen. She smiled to Castle and signaled him to stay quiet as she walked towards Ryan and Aidan, who were playing some silly game on the cop's computer.

The boy loved to scare her by coming upon her from his favorite hiding places, or even startling her when she was reading and wasn't expecting anybody around. Most of the times she knew he was there, but pretended to be scared to the boy's delight. Every time she did it to him, the kid squealed and laughed hysterically, so now it had become a thing between the two of them. She loved making him laugh.

Kate approached them carefully; trying to minimize the sound of her heals against the wooden floor of the bullpen. The two boys were completely absorbed by the game and didn't notice her presence as she stood behind Ryan. She put her hands over Ryan's shoulders and then shook him hard, yelling, "I gotcha, bug! And you too, detective Ryan."

Both, the man and the kid, screamed loudly, Ryan rubbing a hand down his face and glaring at her and Esposito who was laughing so hard he could barely breathe.

"Jesus, Beckett! You almost gave me a heart attack!" The man choked out.

She laughed and moved to the side to check on Aidan, but the boy turned his attention to the game immediately, not giving her a single look or even a hello.

Kate's face fell and she felt a pang in her chest and her eyes stinging a bit. Aidan had never done that, but she thought that kids could act in weird ways sometimes, so she decided to give him some time and wait until he came to her. Because he would, right?

Still a little confused, she made her path back to her desk and Castle, who was furiously typing on his phone and seemed completely oblivious to what had occurred a few feet away from him.

Kate sank into her chair completely deflated and poked Castle to get his attention. "Is there anything wrong with the bug?" She inquired concerned.

Castle frowned and looked at the boy playing happily with Ryan. "Uh… not that I know of. Why?"

"He completely ignored me just now. He didn't even look at me, Castle."

The writer's frown became even deeper and he reached for her hand that was lying on her desk, nervously scratching a crease on the wood. "Hm. That's weird. But now that you say that… He went to look for you at the break room, but he came back a few minutes later looking as if he had seen a ghost."

Kate groaned. "Ugh, Castle. I've told you a million times that this is no place for a kid. What if he saw anything that scared him? He's already having nightmares almost every night. The last thing he needs is to get spooked by some creepy picture he sees hanging around here." She scolded him. "And we will talk about letting him watch 'Mars Attacks' with you the other day."

Castle swallowed the big lump in his throat and nodded, knowing there was no way he could get out of this one. "I'm sorry?"

After clearing her desk and turning off her computer, they said goodnight to the boys and headed out of the precinct and into the freezing New York evening.

Castle's arm was around Kate's shoulders and his other hand held Aidan's, who was strangely quiet.

Kate had started to get anxious about the little boy's behavior, so she squeezed her boyfriend's hand and removed his arm from around her with a reassuring smile before moving to his other side and touching Aidan's head softly, smiling sweetly at the boy when he looked up at her.

"Hey, munchkin. You're very quiet today." She addressed. "And you haven't even given me a hug yet."

She tried to keep all the anxiety and worry to herself, smiling softly, but Aidan just looked at her with his big, blue eyes and a neutral expression on his face.

Kate made Castle stop, putting a hand on his shoulder, and crouched before the kid. "Is everything ok, baby? Did anything happen to you?"

She touched the boy's hand, but he retrieved it fast, as if he had been burnt. He didn't reply to Kate's questions, focusing his gaze on the ground.

"Aidan?" Castle called him. "Are you ok, bud?"

It was all it took to break the dam. The child's eyes filled with tears and he started shaking. He was quiet, though, keeping the anguish inside.

"Oh, damn." Castle mumbled, picking up his son and cradling him against his chest.

He and Kate looked at each other completely stunned, not knowing what to do or what to say to the little boy crying silently in his father's arms.

So? Thoughts? Opinions? Death threats? At this stage, anything would be good ;) Thanks for reading!

Thanks to Tshlw for being the best cheerleader ever and for checking this out for me. All the hugs!