* Growl (http://archiveofourown.org/works/1695626) - John died on a hunt when the boys were young, and they've lived on the fringes of society ever since. (Dean/Sam)

* No Ordinary Boys (http://kc246.livejournal.com/6431.html) - Mary and John Winchester are foster parents, who take in brothers Dean and Sam. Two abused and neglected boys that end up changing the Winchesters lives forever. (gen)

These aren't Sam/Dean and don't fit the parameters, but you might enjoy them anyway, for runaway Sam and Sam-whump:

* Lux Just Ain't For Us (http://archiveofourown.org/works/1007682) - Sam couldn't go home. Lucifer couldn't go home. But that wasn't their home anymore. Their home was the shared sleeping bag under the play castle in the park. Their home was together.

* I Won't Be the Same (http://archiveofourown.org/works/2327294): In 1999, Sam Winchester runs away from home at the age of sixteen. On a bus to anywhere, he meets Lucifer, and the two weave cross-country together in a brief but passionate affair. Now, in 2014, Sam is successful, engaged, and unhappy. He makes one last-ditch attempt to find Lucifer again. He’s got no last name and no address. All he does have is an old picture and the memories of every place they went together. (Lucifer is not Satan, just a kid with a nickname.)