Alright, I read this fic years ago, so what I actually remember from it is very thin but here it is :
It's not an overly long fic, maybe 2 chapters.
It's from Bobby's POV and it starts when the boys are teens. They had always been extremely close and Dean was seriously sick and weak. Sam had been trying to find ways to keep him alive or cure him for years and as the years go, they grow closer and closer, taking codependency to a whole new level, each time Bobby sees them, it's got worse than the previous time. After a while, they break all contact with Bobby for years to the point where Bobby doesn't know if they're still alive or dead, the hunter world is full of different rumors about those Winchester boys. One day, years later, he's on a hunt and this man comes in and Bobby watches him from a distance because there's something vaguely familiar about the guy that he can't pin point. He hears the guy introduce himself as Sean to someone and he just knows that this guy is Sam AND Dean, that the boys somehow found a way to FUSION. I think Bobby mumbles under his breath something along the lines of "Well, I guess you did find a way to keep your brother alive after all, huh Sam?" at the end.
Does anyone know what I'm talking about? It was an amazing fic!
Thanks for your help.

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