There's a "The End" at the last page, and the story feels complete, but then it's listed as "#1." I wonder if there's a sequel planned? Maybe with the new queen deciding to have a male heir after all, just not without the help of a woman? After all, the title is "The Royal Issue," and while it's obviously a pun, we haven't seen any "issue" of the royals yet.
There is an obvious plot hole in this story. If changing one's sex was so easy and well-known in that reality, the king would have just called the sorcerer and had him revert the spell. It should have been explained in text why that wouldn't be an option -- perhaps the magic cannot be reversed before a set time?
Even in such a case, the prince's plan was poorly thought out; even if his bride didn't have a brother, in a context with of magical sex-changes the two conspiring kings could easily had princess Arnette changed into a man.