Fic idea - parallel universe
Furious, she set the Stilinski's house on fire instead, with Stiles' and Scott's parents inside while the boys where at a birthday party (Danny, maybe?).
They all died, leaving Scott and Stiles orphans. Scott was taken in by his aunt, in Nevada, while Stiles was put into the system for a while, before the Hales - Andrew Hale worked with Stiles' dad who was not a Sheriff at the time - took him in.
Stiles got anger management issues, got depressed, rebellious, his grades went down, he started cutting - all in all, he ended up very like the Derek from the "real" timeline.
While the Derek of this world grew up pretty happy (after his older girlfriend suddenly disappeared and he'd gotten over his heartbreak).
Fast forward six years and our Derek and Stiles are suddenly in that universe.
Stiles is horrified by his other self while Derek never wants to leave, wants to stay with his family.
So Stiles has to find a way back alone, debating with himself if he should let Derek stay or take with him.
And then there's this other Derek who makes the decision to go back even harder...
