A/N: Well. This is an idea I had basically from the first time Castiel appeared in "Lazarus Rising". I saw a few fanfictions here of the same concept, but I wanted to write my own version. This is how I imagine Castiel being Dean's angel. Because for me, Castiel knew Dean from the very beginning, watching over him like the guardian angel he is. This is a multi-chapters story.

Summary: Angels were watching him, that's what Mom always said before she put him to bed. He remembered that. Why, then, Dean believed angels did not exist for so long? He wasn't always like that.

I own nothing.

Chapter 1:

The first time he saw him, he knew he was special. Extraordinary. Unique.

His mother was pregnant. He was about to have a younger brother soon, and he was so excited. He helped his father to decorate the nursery, painted the walls – and got paint all over himself, too – and picked toys for Sammy, things he was sure his future baby brother would like. He picked a mobile for him, to hang over his crib.

He was so excited.

He was just in the middle of putting stuffed toys on a low shelf when he heard his mother's slow and heavy steps outside the nursery. He turned around to greet her with a smile, running to hug her knees and rest his head right under her huge stomach. Mary smiled down at him, ruffling his hair with one hand as the other held a small bag.

"What are you doing up here, sweetie?" She asked, her voice melodious. Dean would always remember her voice this way – warm and comforting. He shrugged.

"Making Sam's room cool." He said in his tiny voice, frowning for a second. "Daddy knows nothin' about Teddy-bears, Mom." Mary laughed.

"I brought you something to put on Sammy's shelf." She said in a singsong voice, leaning as if she had a great secret. Dean's big, green eyes lit up in eager curiosity. Mary shook the bag in her hand gently.

"What is it?" The four-years-old asked.

"An angel." Mary pulled a small angel statue from the bag and carefully handed it to Dean. "You had one when you were a baby, too." She smiled. "Well, you know what I always say? Angels are-"

"'Angels are watching over you.'" Dean repeated the familiar saying, smiling brightly at his mother. "Yeah, I know, Mom."

"Now, where do you want to put it?" Mary asked lightly, guiding Dean back to the shelf. "Maybe... next to... Mr. Bunny?" She said in a playful voice that meant to startle her son. Dean giggled. "Or maybe Mr. Teddy Bear?"

"Mom, you can't call all his toys 'Mister'. That's silly." Dean said in a very serious tone, placing the angel at the side closest to the empty crib.

"Oh, I see. So you want cool names." Mary said in a matching serious tone, smirking under her breath at her son's cute and grave face. "Do you want to name Sammy's angel?" She asked. Dean nodded enthusiastically.

"Sure!"

"So, you go and think about a very very cool name, and come back to tell me?" She suggested. And when Dean nodded again, she laughed and pinched his nose where freckles covered his skin like candies, then sent him off to his way.

Daddy took him to the park today. Mom was at the doctor, checking on his baby brother that was soon to arrive. Or so Daddy told him. The park was nearly empty – Dean saw two twin little girls playing by the swings, but he didn't want to go and play with them – he decided they looked mean. And so he stayed by himself and started making a castle of sand, big and magnificent in his opinion – fit for a king or at least a rich lord.

Maybe Sammy would like to play with him when he is a little bit older. And born, Dean reminded himself. He couldn't wait for his brother to be here already. He knew he'd be the best big brother he could ever be. With that in mind, he worked harder on the wet sand, determined to finish his artwork before Daddy said they had to head back home.

Clearing his hands from the drying mud, he stared at his work. He was so concentrated and so proud of his sand palace, he didn't notice the kid that approached him from behind.

"Hello." A small voice said from behind him, and Dean jumped, knocking a wall of sand in surprise.

"My castle!" He called in disappointment, his chin trembling in his attempt to stop the tears that burned his eyes. Boys did not cry.

"I apologize," The kid said monotonously and sat on his knees in front of Dean. He sounded sincerely sorry, and the vibe Dean felt radiating from him was warm and comforting... but not like Mom's vibe. It was different. "Would you like me to help you rebuild it?" He asked. Dean sniffed hesitantly, then nodded.

"Yeah..." He mumbled, watching the other kid flashing him a small, awkward smile.

Dean blinked.

This kid was about two or three years older than him, he figured. He had light brown hair and pale skin, and he was slightly chubby. But what caught Dean's attention the most was his deep-blue eyes. They look like the sea, Dean thought. He remembered how big the sea was. Daddy took him there last summer.

He glanced back to where his father sat. John's attention was all paid to a book he read, though he glanced up from time to time to see if his son was alright. He caught his father's eye and waved, smiling. John returned the smile with an awkward one of his own, then went back to his book. Dean looked back at the older kid, chewing his lower lip.

"I'm Dean." He finally introduced himself, being as polite as Mom taught him to be when talking to strangers.

The kid looked up at him from the castle he helped to repair and tilted his head in a slight surprise, as if he forgot Dean was sitting there right in front of him. His amazingly blue eyes blinked once, twice, and then he offered a mud-covered hand for Dean to shake.

"Castiel."

A/N: Please review and tell me what you think, okay? I really appreciate every review and criticism.

TBC.