Hi Sharleen
I have been very slowly (sorry) checking the BDM records for your family. I have a few changes to the information you have supplied. (I have no idea which would be correct

)
George Aitken died 30 Dec 1882 Ref 1882/B015290 Father Robert Aitken, Mother Isabella Borthwick
Janet Aitken (his wife) died 10 Jun 1910
(you had this date for his daughter) Ref 1910/B012581 Father Thomas Cairns Mother Janet Draper
They are buried in the same grave at Toowong Portion 14 Sect 6 Grave 26
(I will get to take some photographs in the next few weeks)Buried with them is
maybe granddaughter Edith Janet Cairns Hardy (this is name from cemetery list) buried Oct 1883 (Isabella married a George Hardy).
I found the following children
John James Baptism 20 April 1852 Reg 1854/BP2440 parents George & Janet
Janet Cairnes Baptism 8 March 1854 Reg 1854/BP2519 parents George & Janet Cairnes
The remainder are Birth dates (rather than baptism)
Isabella Margaret Bo 14 Jan 1856 1856/B000031 George & Janet Cairnes
Georgina 6 Jan 1862 1862/BA00958 George and Jennet Cairnes
David 28 Mar 1864 1864/B002513 George and Janet Cairns
Marion Moffat 5 Jun 1870 1870/B011221 George & Janet Cairnes
Elizabeth Mary 11 Apr 1873 1873/B015801 George and Janet Cairnes
There is also a death (but no birth record that I found) for
Catherine Alexandra Died 5 Nov 1873 1873/B008089 George Aitken & Janet Cairnes
I could find no birth record for Thomas Cairns Aitken.
If you purchased the death certificate for father George, it may contain a list of all the children as the informant would probably have been his wife Janet, so she should have known all their names & ages.
Trish