Sam/Jess/Dean
From Super-wiki
Sam/Jess/Dean threesome fanfiction pairs the characters Sam Winchester, Dean Winchester and Jessica Moore in a romantic or sexual relationship.
You might also be interested in Sam/Jess, Dean/Jess, Dean/Jo/Sam, or Wincest.
Brief Overview
Sam/Jess/Dean is a particularly popular pairing in AU fics, especially ones in which Jess doesn't die, but joins the boys on the road. Many of these start with Sam/Jess and later include Dean as the three become closer and more cut off from the rest of the world.
