Duncan married Josephine Joan OWENS on 24 Apr 1937 in Bunbury, Western Australia, Australia. Josephine (daughter of Charles Kelsey OWENS and Catherine HASTIE) was born on 25 Dec 1916 in Bunbury, Western Australia, Australia; died on 6 Jan 2004 in Perth, Western Australia, Australia. [Group Sheet] [Family Chart]

1. Neil Stewart MACKELLAR was born on 18 Feb 1937; died on 2 Feb 2017.
2. Isla Joan MACKELLAR was born on 11 Oct 1939 in Harvey, Western Australia, Australia; died on 19 Mar 1988 in Ipswich, Queensland, Australia.
3. Ross Duncan MACKELLAR was born on 25 Feb 1944 in Bunbury, Western Australia, Australia; died on 6 Dec 2002 in Perth, Western Australia, Australia.