Fandom:Buffy The Vampire Slayer & Stargate:SG1
Sometime after the "fall of Sunnydale.
What if , for some reason (maybe an alien illness) while working for Stargate Command, young-adult Dawn Summers finds out her human DNA matches another human's DNA on file (maybe also working for Stargate Command), and it doesn't in any way matches Buffy Summers. That Dawn is the biological sister of Faith.
How did Dawn become Faith's biological sister?
Why did Dawn become Buffy sister instead if she was related to Faith?
In the storyline : Faith still went bad...