Arthur still alive when his wife Harriett passed away - he placed the obituary in The Telegraph newspaper (Inserted by her husband, son, daughter-in-law and grandchildren.)

"She died when Mum [b.1926] was 13" - Cynthia Breusch

QLD gov BDM corroborates with:
Harriet Hargreaves
Event date: 24/09/1941
Event type: Death registration
Registration details: 1941/B/53902  
Mother: Annis Marston
Father/parent: John Mannion

or 1899

Vivian Clayton Hargreaves
Event date: 19/01/1984
Event type: Death registration
Date of birth: 1899
Registration details: 1984/872
Mother: Harriet Mannion
Father/parent: Arthur Hargreaves

Daughters birth cert lists Poppoea as being 22yrs of age on 13 Feb 1926.
Cynthia Breusch recollects DOB as  being April 1903.

QLD gov BDM corroborates with:
Poppoea Coralie Kennett
Event date: 20/07/1963
Event type: Death registration
Registration details: 1963/B/60333  
Mother: Harriet Mannion
Father/parent: Arthur Hargreaves

Rosalie states that PK died in Canungra.