I have possibly located the birth of your father's half brother in QLD..
Born Herbert Victor Grant 1908 QLD to parents Herbert Henry Grant & Elizabeth Birdsall Greenbury..
Herbert Henry Grant & Elizabeth Birdsall Greenbury married QLD married 1906 QLD
Elizabeth Birdsall Grant ? Greenbury died QLD 1909 she is listed as the daughter of Spink Birsall Greenbury & Margaret Ann Andrews..
You have a match..... you are looking for your father and other family in the sate of Queensland...
I will see what else I can locate for you..