It's been a while (like 4 years I think) since I read it. But I'm 90% sure it was under FF (final fantasy) on this site. It was mainly focused on Final Fantasy characters, I think. Here are some other points.
Cloud is/was/was posing as Sora's brother
Sora and Cloud were traveling alone, but join a group
Cloud calls himself Zach I think
I think Cloud was framed for something before the start of the story, and thus can't use his own name
I don't think Sora knew about the above
Any help you can give would be great