There could be the good prince himself. And perhaps there are his loyal servants, a wise old advisor, and the common people in his kingdom.
Well, the main character is of course the good prince. Alongside him, there may be a cast of characters. There could be the poor peasants who look up to him for help and protection. There might be a beautiful princess from another land who he falls in love with, and this relationship could also be part of his story. Additionally, there could be corrupt nobles who try to undermine his good works, and he has to deal with them cleverly to continue his mission of doing good in the kingdom.
In 'the good prince story', we might expect to find the prince as the central character. He could be surrounded by other important characters such as his family members, like his father the king or his mother the queen. There could also be knights who serve him, and villains who oppose his good deeds. Maybe there are also some magical creatures if it has a touch of fantasy, like a friendly fairy who guides the prince on his journey to do good.