Bill, that is true but most likely because Kirk Douglas legally changed his name prior to having any children. His sons are:

Michael Kirk Douglas (9/25/1944)
Joel Andrew Douglas (1/22/1947)
Peter Vincent Douglas (11/23/1955)
Eric Anthony Douglas (6/21/1958 - 7/6/2004 Drug OD)

BTW... Kirk Douglas' real name was changed by his family to Isadore Demsky (to sound more Americanized) which he hated so changed it to Kirk Douglas in 1939.

Eric