So I remember quite a few details of this fic, just not the name or where I left it...
It begins at the beginning of all things the angels are being assigned their first duties, as Gabriel(I think) assigned Castiel guardianship of Thursdays future!Gab flys in and begs that Castiel also be assigned guardianship of Dean Winchester. Other Gab is totally down with that so it's done.
Casitel starts caring for the brothers when they are young boys, even angel mojos Sam around the country so he can keep going to the same school.
At one point of time John finds out and he is crazy suspicious.
Castiel kinda becomes a free agent, though I don't recall if he actually falls.
Anyway, sound familiar to anyone out there?