Summary: Sam had once chosen a demon over his brother, and now he was watching Castiel choose working with a demon over trying to find another way. He had been the one to betray Dean before, and now, he had to watch it again, from the side of the betrayed.

AN: I've seen a fair few Supernatural you-tube vids set to Kryptonite, and this is the byproduct. Enjoy!

His Kryptonite

Sam knew his brother fairly well, but when it came to Castiel the result wasn't always as expected. When it came to family, Dean would roll with the punches, but Sam wasn't sure about this one. Dean kept his eyes to the ground after Cas left, then he turned around, probably so he could let a few tears escape without feeling vulnerable. It was always strange that his brother found turning his back to be less vulnerable than facing things forward. But that was just Dean. Sam glanced at Bobby, the same look of sadness covering his face that likely covered his own.

It had been one thing to think it, it was another to know that Cas had spied on them. Dean would want to know for sure now, and then he would have a tantrum when whatever Cas was doing, Cas refused to stop. He could be incorrect of course, Castiel did seem to have a precedent of ditching duty for Dean, they really couldn't know for sure until they tied him down though, so to speak.

"Well, I'll just go get the Holy Oil then." Bobby huffed out, any enthusiasm drained completely from his stance, and his words. Dean raised his arm to his eyes, then turned around to face Sam. If he hadn't known his brother for so long, he wouldn't have even suspected that any tears had been shed.

"We won't know until he tells us, and he WILL tell us."

"I know Dean."

And then mere hours later, they had Cas locked in a circle of Holy Fire. It was then, that truths came to light which could never have been conceived. That was when spying had been confirmed and guilt admitted by not speaking to the accusation at all. They were the reason he learned to rebel, and they were the reason, Cas had himself convinced, that he was rebelling again. A means to an end, a fix-it in its own right.

"Dean, it's Not Broken!"

Of all the revelations that night, that was the moment that Sam realized just what Cas meant to his brother, whether Dean knew it or not. The look in Dean's eye, he could see it, even standing beside his brother facing the fire… he had seen that look before, not that long ago really. That was also the moment that Sam understood that there was nothing Dean could do, nothing any of them could do to stop Cas. He didn't admit this to himself of course, Winchesters majored in denial after all – Winchesters including Castiel Angel of Mankind it seemed.

Somewhere along the line, Castiel had gone from Angel of the Lord, a garrison captain, to a member of the Winchester family. Cas had become Sam's second brother. Cas had been Dean's savior, and then Cas became his best friend. Perhaps the most tragic of these revelations is that this came to light when the bridges built were already burning down. Dean had the patience and the will to try and talk Cas out of the hole he had dug for himself as he had once tried to do for Sam. Cas didn't take it, he just told them to run.

Dean stayed a second longer than Sam or Bobby had, for one last look. Dean's eyes had shined in the fire only as they could when he was losing hope. They had shined that way when Sam had left for Stanford and when Sam admitted to all that occurred with Ruby. Dean had lost so much, so many times, it was no wonder that he never let people in. But Dean had let Castiel in. Sam learned that night that Dean loved Cas as much as he loved Sam. The only other who came close was Bobby now, but he was a father, not a brother, not a… not a best friend or whatever Cas really was to Dean, Savior, friend, angelfriend, it didn't matter, not now anyway.

God willing they would make it out of this, or rather… fate willing. Fate willing, Cas would learn, and Dean would forgive after much grumbling and much anger. But as kind as Fate had been considering they had seriously screwed Destiny over, Karma seemed to be making the rounds now. Fate willing, this battle of angels wouldn't last much longer. Fate willing, Cas could walk away from his kryptonite, because Dean had just left his, standing in a circle of flames.