James Hammerstein had one child (Oscar Andrew) with his first wife Basia, two children (Will and Jennifer) with his second wife Millette Alexander and one child (Simon) with his third wife Dena (Geraldine Sherman). He died in Manhattan after suffering a heart attack. James Hammerstein Hammerstein was the son of Oscar Hammerstein II, and his Australian-born second wife, Dorothy Kiaora Blanchard. He had four half-siblings, two through each of his parents' earlier marriages: William and Alice Hammerstein, and Henry and Susan Jacobson. The best known of these was Susan, whose husbands included Henry Fonda and Richard Widmark. Hammerstein attended George School in
Hammerstein House Hollywood Historical Society in honor of his late wife Vera Hammerstein. It was his wish that the home be operated as a museum and he contributed many artifacts of his life which form much of the display there. Items on display include Hammerstein's WWI Air Force uniform. The ashes of the home's owners Clarence and Vera Hammerstein reside at the house in two large urns. It was added to the National Register of Historic Places on February 15, 2005. The home is operated as a historic house museum by the Hollywood Historical Society and contains artifacts of the Hammerstein's life.