Aemon Targaryen

Third son of Maekar, born to a Targaryen who never wished to rule and never did. Sent to the Citadel as a boy, chained as an archmaester before his thirtieth year. At the Great Council of 233 AC he stepped aside that his brother Aegon might take the throne, and then took the black to spare the realm any future quarrel over his blood. He served the Night's Watch a hundred years as their maester; he outlived all his line save Daenerys and Viserys, dying at Castle Black in 300 AC at the age of two-and-a-hundred.