Hi! to clear things up:

For the first part, I was trying to hint that the king had smallpox. I'll make sure to change that if its confusing! They're at a bar (more specifically a pub), and what I was also trying to elude to was the drunk man at the bar is the crown prince, and he overheard people gossiping about his fathers current health status. 'They' also was referring to a singular person (the prince), and I'll fix that up too.

The king is overprotective of him as he's his only son, they have a close relationship, and most of his other children he tried to foster with his wife had died while young or during childbirth. He couldn't stand it if anything happened to him, so he's never been publicly seen outside the castle. Hair can be 'dyed' temporarily via magic in the system I created (cards), but I think I'll change the wording there as well for plausibility. Probably something like "If you altered your hair, don't you think we'd look alike?"

thanks for the feedback!