I'm a PhD genetics scientist who used to work in the field of ancient DNA at this place:
Australian Centre for Ancient DNA (ACAD)
They regularly do DNA identification of remains of otherwise-anonymous/unidentified Australian WWI & WWII troops - but a near-relative is needed.
If you contact them, they would very likely be able to help (but it may cost a few hundred quid).
Ask for Associate Prof. Jeremy Austin: he undertakes most of this type of work.
Dean