In homosexual relationships, is there really always a dominant partner and a submissive one? или is that just a stereotype?

In allot of Яой there's semes and ukes. And in allot of media, there's always a еще effeminate partner that's the receiver.
I'm just wondering if those don't really reflect what actually goes on in reality.
I think people think that way because their used to the idea of men and women being together. SO whenever they picture two men together, one of them is playing the masculine role, while the other isn't.
I know there is such a thing as versatility, but i don't really want to end up carrying the wrong idea about something like that in my head.