On Findmypast it looks like in 1920 Hilda Ennis b abt 1895 and Arthur Ennis (son) b: abt: 1920 were travelling from London to Bombay India. Was her husband working there? As they didn't immigrate to Australia until 1922. Interesting immigration records has her son's first name as Martin??? maybe used instead of Arthur (not to confuse with his father)or could be a transcription error. It is strange I have searched electoral rolls for Arthur Granville Ennis but it doesn't appear. It you search Trove Newspapers there are possibly some articles about your Arthur Granville Ennis. Search using "Arthur Granville Ennis" and also "Arthur Grenville Ennis" If this is your family member then it appears he had a difficult life. I have tried searching for Hilda after Arthur John's death in 1950 but no luck - again not on Electoral rolls under Ennis perhaps she remarried.
Also found on Australian National Archives - Passenger Arrivlas 1921 -1949
Ship: NALDERA Departed: Bombay Arrived: Fremantle 10 Aug 1922
Mrs H ENNIS
Mr A J ENNIS
Mstr Martin A G ENNIS