Hello again,
Having put Jane ? aside for the moment, I have been doing a bit more digging...trying the 'thinking outside the square' approach.
Having found no death record for Peter Cameron pre 1865 in the non Catholic records in SP, I checked their Catholic records and found that a Peter Cameron, born Tombreck, died in Australia (small world moment...) on 3rd July 1862. I checked the Australian death records and found him in Victoria. His occupation is not given, however age is given as 35, born in Banffshire, parents are Donald Cameron, mason and Charlotte. He has been in Victoria 8 years so arrived approx 1854. He was unmarried.
Libindx has his baptism as 18 Apr 1827, parents Donald Cameron, mason of Tombreck and Charlotte Middleton, matching those 1841/51 Census' for Donald & Charlotte. Donald is his father rather than his brother, and died in Tombreck 5th Jan 1856 (also from the Catholic registers). Charlotte died 20th Feb 1874.
I found what looks to be Peter (mason) in the 1851 Census, listed as a visitor in the McGregor household, Auchindrine, Aberdeenshire. The fact that we haven't found him in successive census' would support his going to Australia.
Now, Donald Cameron married Charlotte Middleton 5th June 1821 and their list of children on SP includes Peter, 18th Apr 1827.
Donald Cameron's entry in Libindx has his parents as James Cameron, born abt. 1755, death 13th Nov 1816 and Isobel Stewart, death 11 Dec 1829. James & Isobel's list of children includes Donald, with a brother William.
Brother William's Libindx entry has him marrying one Penuel Middleton 22nd June 1820 and the list of children to William Cameron and Penuel/Jannet Middleton includes a Donald born 18th March 1823. It seems that brother and sister have married brother and sister. Both Penuel and Charlotte's death records list parents as John Middleton & Mary Cameron, although the father is incorrectly named as James on Charlotte's libindx entry.
This could mean though that the Donald Cameron, informant on the death certificate of Robert Cameron (1865) is actually his father's cousin but he has thought it easier to call himself uncle. However, I have still not been able to find his death record.
Does all this sound plausible??