Many of us may not know that two of the sixteen classical prophets in the Old Testament were from royal families.
By the way, classical prophets is a technical term for the prophets whose names we have books, like Isaiah, Amos, Jeremiah, etc. At the same time, despite their antiquity and prominence, Elijah, Elisha, Gad, or Nathan do not fall in this category since we do not have books in their names.
The classical prophets came from a variety of backgrounds. Biographical information on most of the prophets is scanty. Still, we know Amos was a farmer and a sheep breeder, while Jeremiah and Ezekiel were priests.
The two prophets with royal connections are Zephaniah and Isaiah. The Book of Zephaniah introduces the prophet as a descendant of King Hezekiah. "The word of the LORD that came to Zephaniah the son of Cushi, son of Gedaliah, son of Amariah, son of Hezekiah, in the days of Josiah the son of Amon, king of Judah" (Zeph 1:1). But there is nothing in the rest of the Book to confirm the prophets connection with the royal establishment in Jerusalem.
In contrast, Isaiah's connections with the royal establishment are not directly mentioned. Later Jewish traditions suggest that his father Amoz was a half-brother of King Uzziah, who ruled in the eighth century. However, ample clues in the Book of Isaiah lead us to believe that this later Jewish tradition about his royal connection is valid.
First is his easy access to the kings in Jerusalem. He could meet with King Ahaz when the king was out to check the water level in the upper pool near the royal quarters (Isa 7). He could visit the sick King Hezekiah in his bed room twice (Isa 38). King Hezekiah sought his spiritual help by asking to pray in times of crisis (Isa 19:1-7).
Secondly, he knew about the discussions in the royal cabinet, which commoners had no access to. The military threat from Aram and Northern Israel had made the king and his cabinet nervous, so they "shook as the trees of the forest shake before the wind" (Isa 7:2). He knew that Hezekiah was making futile plans by sending his diplomats to Egypt to seek alliance and military supplies (Isa 30:1-7). He also knew that Hezekiah had foolishly displayed his wealth to the visiting Babylonian envoys (Isa 39:1-8).
In addition, his message shows he was well-versed in international politics.
So, Isaiah was a prince in Jerusalem who, like all other classical prophets, proclaimed judgements against the reigning monarchs when they acted against the will of the supreme ruler of the world, the Emperor, the Lord.
(Based on insights from my recent book, THE PRINCE AND THE EMPEROR. SELECTED THEMES FROM THE BOOK OF ISAIAH, now available on Amazon globally.)