I read this fic a while ago, and the only things I cannot remember is the title and author. 

Dean is going to college, and he's on his last semester, or something like it, and he only needs one class, a Literature class which Castiel is the professor of. Castiel's parents studied angel's and such and that's how he explains his and his family's strange names.

Very slice of life.

Dean almost quit's school because he and Sam need a place to live because John is a drunk (after Mary dies?). They end up living with Castiel.

One of Castiel's brothers has the broken down Impala, which Dean fixes up during his free time at Castiel's house, he ends up being allowed to keep it.

Dean ends up really liking Shakespeare and Sam gets a dog I think.

Castiel helps Sam with his college applications.

OH, At one point Castiel is having a lunch or something with Anna, and Dean thinks Anna is his girlfriend, when later he find out that she is Castiel's sister.

Everyone is a big happy family at the end, and I really want to re read this baby.

I have a feeling I read this on AO3, but I could be wrong.

(i tagged with everything i could remember about the story, i apologize if i didn't get all the characters in)