They hold their child for the first time:

Dean:
Dean rocked the baby back and forth in his arms. He couldn't believe this child was his. She was the cutest little kid Dean had ever seen.

"Hey," he said, looking at the babies gorgeous eyes. "I'm your daddy. I'm going to teach you lots of things, but don't tell all of them to your mommy."

Dean glanced over at you asleep on the bed. He wasn't here when his daughter was born. You had named her Natalie Marie Winchester. Dean was on a hunt with Sam when you went into labor. He nearly screamed.

You heard a yell and then a crash form the other end of the phone. Then you heard Sam yell at Dean to focus. Dean told you he'd be there as soon as possible.

Now he was here and loved it. Natalie reached her tiny hand to touch Dean's face. He sat down in a chair and held her close, closing his eyes. All he could think about was the wonderful child he now had, with the best person he had ever met.

Sam:
Sam held a tiny little boy in his arms. The child was the smallest child he's ever held. The baby looked so tiny in his arms.

He looked over at his wife, Y/N. You were awake and watching Sam hold your son. It was the cutest thing you'd probably ever seen.

"He'll be such an amazing kid." Sam said, laying on the bed next to you, your son now upright on Sam's shoulders.

Castiel:
Castiel was confused. He'd never had to do anything like this before. The little girl in his arms was so tiny. Her hands were about the size of a medium sized bouncy ball.

She started fussing in his arms, trying to get comfortable. Castiel tried adjusting her, so she didn't start crying and wake you up. She started crying anyway, which woke you.

"Need help?" You ask groggily.

"Um, no Y/N. I'll be okay." Cas said, still trying to steady the fussy baby.

"You sure?"

"Yes."