Hiya,
I gather from info in here and your tree you are looking for this man..
STUART-SUTHERLAND ROSS ALLASTAIR : Service Number - 32128 : Date of birth - 25 May 1906 : Place of birth - AVNAGALIAN SCOTLAND : Place of enlistment - SYDNEY NSW : Next of Kin - STUART-SUTHERLAND DOROTHY
Do you think he and Roy are one-in-one?
Kellie