RIP.
I always thought the question of whether she and Michael Keaton were related was an interesting one since neither were able to use their real names in Hollywood. An article revealed that online searches for Michael Keaton have surged since Diane died, likely due to people checking to see if there was any relation.
Diane Keaton was born Diane Hall, but there already was an actress with that name so she took her mother's maiden name as her last name. Michael Keaton was born Michael Douglas, but of course there already was an actor with that name, so he took the last name of Keaton after picking it from the phone book and thinking it sounded suitable. (Just recently he announced his intention to go by Michael Keaton Douglas for future roles).