I think he was born Keith MUTTON...and I'm not sure if his mother did a runner or if she divorced but she ended up marrying Matthew Henry MURRAY in WA in 1898.
NSW BDM info.
4805/1890 MUTTON HAROLD A to WATTS NELLIE at MARRICKVILLE
32755/1892 MUTTON KEITH HAROLD A NELLIE ST LEONARDS
29777/1891 MUTTON EDWARD A HAROLD A NELLIE RANDWICK
36358/1894 MUTTON MARJORIE HAROLD A NELLIE WAVERLEY
MURRAY MATTHEW HENRY to WATTS NELLIE at KALGOORLIE 1898
You can check other children on WA BDM