I think if you stretch the terms dominant and submissive, all marriages have an element of it. Maybe one is dominant over one area of the relationship while the other is dominant over another. Like maybe the man is the one who dominates the family budget while the wife dominates the home and it's decor and meal planning. Ever hear the terms "hen pecked or worse... pu$$y whipped? I think many households have an element of them but the couple does not even give it a name. It's just the way it is. Even the hen pecked husband won't admit to it. lol
BTW, my SO and I both dislike the term MISTRESS and don't use it at all.