Has it ever been explained how Aeris and Leo are related to each other? Are they siblings? Roommates? Cousins? Boyfriend/Girlfriend? Or is it left deliberately vague?
With all of the ship teasing over the course of the series, and that they apparently met for the first time in school where Aeris seemingly developed a crush on Leo, they probably aren't related. (Of course Solid Snake was bullying her, so any canon that strip represented is up for debate.)
They definitely aren't related, but they've known each other for a long time.