>>91078105>all past rulers have been queens
T.b.h. I've been under the assumption that they've only had first born female successors or heirs, as unrealistic as that sounds (not that it would be the first show to do something like this, either).
Or that they have a rule that says to limit the amount of children to one each generation, due to only having one family wand and in doing so it would stop any struggle for power that would occur with multiple children.
So there's a few scenarios that are possible:
1. Only Female successors have been born up to this point in time
2. There is a limit on how many kids a Mewman can have biologically or legally as ruler
3. Only females can take throne
Scenario two is a given, since there's only one wand and its unlikely they will or could ever create another one
River took her name because she's from the royal line, not him. He comes from a clan of warriors. So it only makes sense that he'd have to take her name.