Human beings are so fragile. Castiel asked Dean why, but he just laughed. He thought Cass' question was stupid, and Dean believed himself was not fragile. He knew Dean lied. Castiel had seen the Winchesters breaking down so many times, especially Sam. He was dying, hurting, he had been to hell, and the trials one time made him terribly sick.
Every time he was with Sam, he count every beat Sam's heart made. The sound of a heartbeat, it was fragile, too. He always had the fear of one day, any beat could be Sam's last.
Dean had been gone since noon to get some fast, unhealthy food, while Sam was stubborn enough to stay at home cooking his own food.
Cass got up on his feet, and walked to the kitchen. Even though angels didn't need to feed, the smell of whatever Sam was cooking was irresistible.
"Hey Cass, you want some tomato soup?", Sam turned around when he heard Cass' footsteps approaching, but his hand was still holding the whisk, steadily stirring some kind of red liquid in the pot.
"Sam... I'm not..."
"Come on try it!"
Sam smiled. It had been so long since the last time he saw a true smile on Sam 's face. He had been through so many things that no ordinary human could ever think of. Still, he was here, a little broken but alive, and his heartbeats still went on.
Sam handed him a bowl full of red liquid. It was hot, and smelled good.
"What is this?", Castiel asked, "It smells better than those things Dean usually eats."
Sam didn't answer, but another smile appeared on his face.
"Seems like it is made from...hmm...tomatoes, isn't it? I remember the first time Father created tomato, all of us thought that--"
"Hey, just taste it!", Sam chuckled. He ran his left hand through Cass' hair, and put a gentle kiss on his forehead. Castiel guessed that was what people did when they wanted someone to eat their food.
It was good, the soup was good. Sam told Cass that was tomato soup, otherwise he'd keep calling it 'the red liquid'. He felt 'full', Sam did too because Sam had said that earlier. He was so certain that he was full, but Castiel didn't believe it. He ate more than 5 bowls of tomato soup, while Sam only ate 1. He thought that might be the reason why humans were not so strong.
They were sitting on the couch, watching some little kids cartoon, because Castiel liked cartoon. Sam was right next to him, Cass could hear him breathing, slowly and gently. Sometimes he laughed at the stupid cat in the show, sometimes, he just looked out the window to check if his brother was back.
That moment when Sam looked out the window, his chest touched Cass' ear, and Cass could hear his heartbeats. They were so loud, so real, much different from the beats he had heard using his power. They were... lively.
Castiel laid his head on Sam's chest and closed his eyes, he wanted to feel every of the beats from Sam's heart. Sam lowered his head, looking at Castiel with his beautiful eyes, then slowly put a kiss on Cass' cheek. Sam was not suprised at all, like he already expected that Castiel would do this.
"Cass?", Sam once again ran his hand through Castiel's hair, he liked to play with those little curls, "What are you doing?"
"I'm listening to your heartbeats."
"What for?", he smiled, and his eyes lightened up just as beautiful as the stars.
"I'm scared that one day it would be your last. And then, you'll leave me.", Cass close his eyes, tried to stay close to Sam's chest, to his heart. Who knew what would happen if he got careless in one moment?
Sam remained silent. He was thinking. He thought about everything he and his brother had been through. He wondered how on Earth they were still alive, still in one complete piece. And he thought who knew when his heart would make its last beat, maybe next week, or tomorrow, or maybe tonight. No one knew.
"Hey, I'm not going anywhere, not now. Castiel, as long as you are here, then I'm here. Okay?"
Sam whispered, words by words. Of course, Castiel heard them so clearly, and they comforted him.
"Okay.", Cass answered.
Sam gently placed his lips on Cass'. They were so soft, softer than the clouds, and so sweet, just like the apples in The Garden of God.
Castiel were sure he just fell in love with Sam Winchester.

Dean had got back while Sam and Castiel were cuddling on the couch, watching the last episode of Prison Break season 1. Still holding Cass in his arms, Sam looked out at the front door, where his brother was standing.
"Hi, Dean!"
Dean stared at him for a couple seconds, then smacked his tongue, "Dude, really? In the living room? Could you two be more gay? No don't answer me. I'm going to bed."
Sam laughed, just like a little child. And Castiel knew, that he would have to take care of these two kids for a really, really long time. He would have to listen to Sam Winchester's heartbeats every second. And yes, Castiel would love to do it.