Here’s this, Feed the Crown, 2D platformer where you have to collect food for your queen, you can choose one of the three, Pig Queen, Bird Queen and Mouse Queen.
Yeah, I’d say your best bet would be keeping an eye on Royal Banquet.
The vast majority of games have you playing as more common folk; adventurers, bounty hunters, and the like. It’s tougher to make a royal the protagonist because they can kinda already go wherever and do whatever they want, not much sense of achievement…
It’s certainly doable, but it requires a little more thinking outside the box with the game’s concept.