Aemon Targaryen

Aemon, born Aemon Targaryen, was the third son of King Maekar I Targaryen and his wife, Queen Dyanna Dayne, the younger brother of Daeron and Aerion Targaryen, and the older brother of Aegon V and Rhae Targaryen. Due to an excess of Targaryen heirs, Aemon was sent to the Citadel in his youth to train to become a Maester, eventually joining the Night's Watch, alongside his grand-uncle, Brynden Rivers, to serve as the Maester of Castle Black. Aemon served through a dozen Lord Commanders, including Brynden himself, remaining at his post even after the destruction of his house during Robert's Rebellion. He eventually passed away at the age of 104, shortly after the election of Lord Commander Jon Snow.