Hi Kellie,
Your statement is correct (as always). .... "TROVE has a death notice for the Daniel who died 1923 Granville and it states he was 78yo, so born around 1845, give or take a few years."
From Rookwood Independent Cemetery website, the brother and sister (Daniel and Barbara) are buried together.
Deceased Details
Surname MC VICAR
Given Names Daniel
Age 77 Y
Date of Death 10 Nov 1923
Date of Interment 12 Nov 1923
Denomination Presbyterian
Section 6D
Grave Number 0011216
Other Deceased
170632 : GRAHAM , BARBARA
Surname GRAHAM
Given Names BARBARA
Age 87 Y
Date of Death
Date of Interment 24 May 1935
Denomination Presbyterian
Section 6D
Grave Number 0011216
Mary