I have a very silly au where Zack is sent to Fort Condor instead of Nibelheim and asks Cloud to take care of Sephiroth (partially as a joke, partially cause he doesn't want to have to hunt down Sephiroth for Shinra if he defects).
Meanwhile, Cloud takes his request Very Seriously, to everyone presents amusement. Sephiroth is just kinda humoring him at first until he's locked himself in the basement of Shinra manor and Cloud keeps dropping by with food and water and dragging him away from his depression spiral to *gags* walk outside and talk to people 🙄 like who does this trooper think he is? Sure, the soup was good, and the blanket was warm and his eyes are kinda tired from the strain of reading all those research documents ....
Cloud, frantically texting Zack and Kunsel copies of everything while Sephiroth sleeps: Never ask me for a favor again, I don't get paid enough to understand what's going on here.
Kunsel: ???? Where did you find this???? All of this is insanely classified, Dr. Crescent's research was buried after her disappearance 20 odd years ago.
A very eventful and informative email chain later, and the trio fully uncover Sephs' actual parentage through some old photos and some light corporate espionage. Sephiroth wakes up a little less on edge and is informed that; Yes, he is human, No, he's not an Ancient, No, the person/thing in the reactor is not his mom or even actually an Ancient, Yes, hojo is a lying bitch, No, he shouldn't burn everything to the ground because that weird little freak would probably like that and Nibelheim folk thrive on spite also oh yeah you're technically from here so you're a country boy too!