I wrote one kind of like this a while ago - it's called the Angel in the Woodshed. http://amberdreams.livejournal.com/63933.html

thanks!!

That's probably not exactly what you are looking for, but it's a great fic and it does contain protective!Cas and young!Sam and Dean. It also contains Weecest, Wincestiel, non-con (though not between the three of them) and slavery.

Save me (http://archiveofourown.org/works/514566?view_adult=true) by saltandbyrne.

Captured and sold into slavery, omega brothers Sam and Dean are the main attractions at Alastair's. When they aren't fighting in the pits or warming the beds upstairs, they find what comfort they can in each other's arms. Castiel Novak, an alpha with a talent for killing and taking down the omega slavehouses targeted by his family, takes one look at Dean and knows he'll do whatever it takes to make Dean his. But when Castiel learns just how close the two brothers are, and just how deep their wounds run, will he be able to love them as they are?

thanks for the post!!

I don't know if this exactly fits, but it's a great story - very long, a wip, but author posts frequently. It has deaged dean, and cas protects him and his family. The boys aren't abused, but Dean has a knack for trouble finding him.

http://archiveofourown.org/works/1413922?view_full_work=true (If I Knew Then What I Know Now by whatUseeintheshadows)

thanks!!!

I literally just finished this one and came to search for more!
http://archiveofourown.org/works/3207881
Not abused but is cas looking after sam and dean when deaged (dean 6, sam 2).
You wouldnt happen to have the link for the cps one you mentioned would you?