Fanonically? Remus Lupin. Canonically? Jo says that he was a hearthrob in his days at schools, and we are led to assume that many girls liked him and that he was popular. we are never told if he had an actual 'love interest.' Fanfiction has other ideas.
Only like every single pubescent girl in the fanfiction freaking Harry Potter society, either that or it's about Draco or Snape. You obviously don't read very much fanfiction.
