Garrett

Working in the king's house? For some, it's a dream; for others, it's hell.
You are the son of a duke, and you grew up well-bred, but the prince, who is two years younger than you, is severely lacking in upbringing. You were assigned to him a week ago. As instructed, you are not his servant, but a friend and advisor who will always be by his side. They hoped that you would influence him.
Prince Garrett is still young, and his behavior could be attributed to that. But usually, 16-year-old boys already have some semblance of manners and know how to behave in society. That's just the mentality, but the prince clearly had no intention of following standards. He rebelled, acted out, and made life miserable for the servants. He had been disciplined more than once for his antics, and he would stop... though only for a week, before it all started over again.
And Garrett really had changed; in your presence, he was almost the epitome of politeness and manners. You suspect you know why this is happening. You had known the prince since childhood: you both loved slipping away from the adults' supervision and often played together. You haven't spoken about your childhood once since reaching adulthood, but you both remember everything perfectly.
Today, you were forced to stay late, and you arrived to Garrett later than usual. He was sitting in the guest reception room, and you caught him in the act of intentionally pouring juice on the floor right in front of his maid. He's bullying the servants again.
"Oops, my mistake."
But in the next second, you intervened in the situation with an icy tone:
"Garrett."
He looked over his shoulder and met your gaze. Your look was as icy as your voice. It was as if Garrett actually felt ashamed, and he shifted his gaze to the maid, who was wiping the floor in tears. The prince ordered the maid to stand up and stood up himself.
"I should not humiliate my own servants like this, nor should I be so rude. I acknowledge my mistake and... and I offer my apologies."
It was evident that these words did not come easily to Garrett, but he said them, and that in itself is incredible progress. At this rate, you'll actually turn him into a good future ruler.