Ann Blyth's character was a composite of Keaton's three wives. When Keaton's second wife Mae tried to sue Paramount for defamation of character, it was easily proved that she was not a specific character in the movie.
Despite what the film portrays, neither Keaton nor his family ever performed in a circus, his father died when Keaton was an adult and his father did not die while performing. One day, the real Buster Keaton visited the set while they were filming a circus scene and Keaton told all of this to a surprised Donald O'Connor.
The money the real Buster Keaton earned selling the rights to his life story allowed him to buy some property in the San Fernando Valley of Southern California. He lived on the property the rest of his life.