Thank you all for you interest and response.
I thought I should just clear up what I know as far as dates etc are concerned.
Firstly the idea that Peter and James are brothers is supported only by family lore and circumstantial evidence hence my reason for wanting to trace parents. James was the original settler here of a family line that went on to be big owners of land/horses, started a legal practice, had amongst its line a QC and and MP....of course I am descendant from Peter...the line without money
The dates and history as I know it are as below (hope this isnt too long winded)
James Purves (occupation, architect/engineer) arrived Van Diemens Land (Tasmania) prior to 1835 to build/supervise stone bridges, then moved to Melbourne in 1837 ("Land Lime Leisure by Charles Hollinshed et al 1982, pub Shire of Flinders).
Peter Purves (stone mason) arrived Van Diemens Land (Tasmania) 1835 to help his (alleged) brother James with bridges. Peter moved to Melbourne 1842 (intra coastal shipping records).
Peters wife Barbara died in child birth, child James b 29 Sept 1835 and sent to live with aunt (surname Russell?) in Berwick.
James (son of Peter) arrives in Melbourne to join his father 1852 aboard the Thomas Lawry left Aryshire August 1852 (inward shipping records).
A strange coincidence re the Cairns family in the Census record.
When Peter Purves settled in Melbourne, another well know family in the area was a Cairns family. In fact I had a great aunt who married one of the Cairns men.
