Who is the proprietor of the House of Usher? How does he and the narrator know each other

Roderick Usher is the last living descendant, along with his ailing sister Madeline, of the Ushers, a time-worn family of wealth and prestige, known as patrons of the arts and givers of charity, but also stricken with a peculiar temperament that seems to run through their blood. We learn that the Narrator and Usher were childhood friends.