Equivalent to the emperor's grandson, but historically they belong to our vassal state of China. Their king can only be the king, and the level is the county king. Their heir to the throne can only be a prince, whose son is a grandson; In addition, correct, since you are the king, you can only be addressed as your highness. According to the traditional regulations of China, the emperor is addressed as Your Highness, while the Crown Prince, Prince and County King are addressed as Your Highnesses, but there is no honorific title. The Li Dynasty created the honorific title and honorific title of the mansion, so their prince was honored as the mansion, and his son was the grandson of the world.