It was Rywalk and after they started hooking up, Jon thinks that Ryan is cheating on him with everyone from TAI until he realizes that Ryan has a slutty twin that no one knows about. It was a chaptered fic that was more of a universe than a chaptered, fic, actually. Everyone called Ryan's twin 'Ross' and there's a chapter where Ross dresses up in a schoolgirl uniform for someone's birthday. One of the last few fics she posted was one where Pete realized there were two Ryan's and attempts to steal them away. Thanks in advance!