I think that Storm is the alpha in my house. He acts like he's the mother to Sunny and Pepper. If they leave the litterbox untidy, he'll go in and tidy it up for them. If he wants a drink he'll push Pepper or Sunny out of the way. I've also seen Pepper push Sunny out of the way to get a drink. I haven't seen them fighting over food though. Storm will also be the one to start attacking Pepper but Sunny seems to be the one to start attacking Storm. I don't think that any of them are always in the dominant role though.