He is Yukio and Rin's grandfather in the Blue Exorcist anime only.
He is Yukio and Rin's grandfather and the father of their mother, Yuri. He explains to Yukio that the Council of Gregori executed her after the Blue Night.
Ernest, who is created by Kazue Kato, has no information regarding any inspiration used to create him. He first appears in Blue Exorcist episode 20 and does not appear in the manga. His Japanese voice actor is Toshihiko Miki.
After Shura and the exorcists arrest Igor and find out that the masked intruder is Igor's wife, Yukio sits outside wondering why he cannot save his brother. A man takes Yukio to meet Ernest, his grandfather.
Ernest explains that his daughter, Yuri (mother of Rin and Yukio), was executed by the Council of Gregori who wanted her existence erased. After surviving the Blue Night, he reveals Yukio, the dragon factory where it houses weapons that destroy demons.