Knew Viserys from Aegon

Who knew Aemon Targaryen was still alive and on the Night's Watch?

TL; DR - I doubt Maester Aemon has not thought much of those who play the Game of Thrones because of the vows he swore and his advanced age.


First a quick story ...

Aemon was the third son of King Maeker I and, as such, decided to train as a maester as he was unlikely to inherit the throne. The decision was also cemented because a maester's surname, title, etc. are stripped as soon as he forges a chain. This did not prevent some from using Aemon during the Great Council of AD 233. To be raised to king. During this time, Aemon decided to join the Night's Watch in swearing a second vow not to hold titles in order to further distance itself from Westeros politics.


So it is likely that the following groups or individuals knew about Maester Aemon:

  • The night watch : Jeor Mormont and therefore probably others higher up in the ranks of the Night Watch. After a few conversations, Jon finds out Aemon's true ancestry.

    Aemon rightly knew that if he stayed at court, those who didn't like his brother's rule would try to use him, so he came to the wall. And here he stayed while his brother and his brother and son's son reigned and died one after another until Jaime Lannister put an end to the Dragon-Kings line. [Jeor Mormont to Jon Snow] - A Clash of Kings - Jon I

  • The Maesters of the Citadel : We see Alleras and Marwyn know about Aemon's story.

    He was more than just the oldest living maester. He was the oldest man in Westeros and had more history than Archmaester Perestan ever learned. He could have told us a lot and more about the reign of his father and uncle. [Alleras vs. Samwell Tarly] - A feast for crows, Samwell V.

    The world that builds the citadel has no place for sorcery, prophecy, or glass candles, much less dragons. Wonder why Aemon Targaryen was allowed to waste his life on the wall when he should by law have been raised to be an archmage. His blood was why. He couldn't be trusted. Not more than I can. [Marwyn to Samwell Tarly] - A feast for crows, Samwell V.

Since this is the organization that Aemon is directly connected to, this makes sense. I found no evidence that other people in the realm, even King Robert, knew of Aemon's ancestry.

Möoz

IIRC, Aemon mentions to Jon that he has not entrusted his Targaryenism to most people.

Aegon

@ Möoz He didn't say that. He just told Jon that he was only using his first name according to his order's vows which compel him to give up his last name. Senior officers and those who knew him must have known. Jeor Mormont knew without a doubt.