This theory is from TV Tropes. If you watch “Curse of The Flying Hellfish”, you see that Sheldon Skinner looks like Armin Tamzarian. The reason for this is because at some point before joining the Flying Hellfish, Sheldon Skinner had spent some time in Capital City and had an affair with a hooker named Ms. Tamzarian, this resulted the birth of Armin Tamzarian, which would make the real Seymour Skinner and Armin half-brothers. Sheldon abandoned Armin before he was born to join the Flying Hellfish. Shortly after he was born, Ms. Tamzarian gave Armin to Shelbyville Orphanage. I think it's a really good theory and explains a lot. I know in one episode Agnes was shown pregnant with Seymour at the Olympics, but how de we know it was Armin? It could've been the real Seymour Skinner from “The Principal and The Pauper”. And all flashbacks showing a kid Seymour with his parents was also the real Seymour Skinner. They are half-brothers, so looking similar to each other isn't impossible. What do you guys think?