After me, it's Thomas and Turbo (two cats). I don't know which one of them is alpha. Turbo likes to tell everyone else he's in charge (except Thomas), but Thomas walks around like no one is going to mess with him. He does that everywhere-other people's homes, Petsmart, etc. He walks around fluffing his tail like, "This is my place now."
So Thomas, Turbo, Sadie, Riley, then Bevo (my third cat, brother to the other two). Bevo doesn't have any dominant ambitions. He'll let the dogs know if they bug him too much, but usually, he just runs and jumps up somewhere.
My ex-boyfriend has cats, too... sisters. Macy Bean (hence the screen name that I've used for years) is dominant (was over my cats and Sadie, too; this was pre-Riley). Ilya always had to defend her number two position to Thomas and Turbo, yet she seems to think she's the queen of everyone, people included. She'll nip at you if you pet her "wrong" or stop petting her before she wants you to. Bevo would jump up on the bookcase with her and roll over, submissive like a dog. He'd "talk" to her the whole time, and she'd bat at him a couple of times, stay for a while (to show him she's still dominant, I guess), then leave. We think Bevo's just a little crazy.