To anyone who is currently reading this series: Umm, no, this guy is not the prince.. He's the King. I'm not sure why would ppl think that Your Majesty refers to a prince, it's for a king or queen. You use Your Highness for prince's and princesses.
Diana even mentions that the Ineer Palace is also a part of the king's responsibility, why would she mention that right then if he was the prince. Also, in chapter 1, there's a mention of that guy actually refered by Diana as the king.
TL;DR no prince yet, but there's a King.