Familysearch has this.......
Alexander Cameron married Elizabeth Marks on 4 July 1836 at St.Thomas Port Macquarie, New South Wales.
Groom born 1807. Age 29. Bride born 1812. Age 24.
There is also an Ancestral File on FS which states....
Alexander born 1807 Scotland. Death 12 Feb 1880 Walcha,New South Wales
Elizabeth Marks born 1812 Ireland. Death 16 March 1890 Walcha,New South Wales
7 children.....
Wiiliam born 17/8/1838 bapt 28/10/1838 Lake Innis Farm,New South Wales. Death 1/1/1904 Port McQuarie,New South Wales
David born 8/8/1840 Port McQuarie,New South Wales. Death 5/5/1841 same location
Alexander born 1844 Port McQuarie,New South Wales
John born 26/4/1837 Port McQuarie,New South Wales. Death 29/3/1915 Walcha,New South Wales
James born 7/3/1842 Port McQuarie,New South Wales
Mathew Arnold born 17/12/1848 Kirial,New South Wales. Christened 8/9/1850 Yarrowitch,New South Wales. Death 30/8/1929 Walcha,New South Wales
Robert born 1846 Hastings,New South Wales. Death 21/3/1937 Armidale,New South Wales