Set champion select order

Ok so I play 5 man games with my friends and there is one little thing that annoys me. I'm always first pick. I don't know what causes this to happen and to refute any arguments that might be made: no, it is not because I am the team captain, many times my friends invite me to game and I'm still first pick, and no, it is not based on MMR because my friends have higher ranks than me and some have lower ranks than me, and no, it's not alphabetical order. So I'm very curious as to how champion select order is decided, or if riot's RNG sucks, because 99% of games with my friends in a 5 man premade, I'm first pick and it's very annoying having to be counterpicked every single game when I want to play with some friends.