The Winchester's Guardian

Castiel has been waiting forever to finally become a guardian angel for humanity.
He has trained for millions of years, studied them carefully. Even walked among them a handful of times, watching them.

And finally, Castiel has been assigned to a man; Sam Winchester.
Being a Guardian is a large enough task, but it gets more difficult still.
Castiel has to fall in love with Sam, so they he is willing to give himself totally to him and protect him no matter the cost.

Castiel befriends Sam easily, after all, they are a match made in Heaven itself.
But Castiel finds himself forcing the attraction between them, not involuntarily as his superiors told him he would.
They had said it would all fall into place.
But that's not the case.

Until Samuel introduces him to his sibling, Dean Winchester.

And Castiel is so entranced he immediately realizes;
He's been assigned the wrong brother.