He started with 4 and now every movie there's a few more.
Sorry, Bro, there were only three in the original chain. A dude and two chicks. Even with the dogs, there were only 3.
As for Six being genius, hardly. Want proof, go to his website and see what he is peddling as art. He simply came up with an idea that he knew would gross people out so he made a movie that failed to deliver on that promise, knowing that people would see it just for the gross factor, then he made a second that was ridiculously over the top disgusting and stupid then tried to play it off like it was some sicko's fantasy. Yeah, I will likely watch the third one, just to see the doctor is up to, but personally I thought the idea ran it's course after the first film.