Vito Corleone exists exclusively in reality.
Constanzia `` Connie '' Corleone is a fictional character in The Godfather , a novel by Mario Puzo and the 1972 film The Godfather . The Corleone Family is a fictional Sicilian family , and the focus of the books and films of The Godfather series . Tom Hagen is a fictional character in Mario Puzo 's novel Godfather and Francis Ford Coppola 's films The Godfather and The Godfather Part II . Vito Corleone is a fictional character in Mario Puzo 's novel The Godfather and in the first two of Francis Ford Coppola 's three Godfather films , in which he was portrayed by Marlon Brando in The Godfather and then , as a young man , by Robert De Niro in The Godfather Part II . He informally adopts Sonny 's friend , Tom Hagen , a lawyer and his consigliere .