A Public famiy tree on Ancestry lists Thomas John Forbes' birth as 29 December 1829,London.His marriage to Margaret Petty 26 April 1853, St. Francis RC Church, Melbourne, Victoria. Margaret's birth place is given as Kings County, Ireland in 1829.
Another Public tree lists Thomas's birth as 1830 London, whilst his wife is named as Mary Eileen Petty, b 1829, Ireland.
However-
There is an interesting entry in 1851 census for a Thomas Forbes living at 6 ???? Vale, Camberwell , employed as a solicitor's clerk. (Born 1830, Road City, Middlesex)
Louisa Partington 37
Thomas Forbes 21
Emma Louisa Paton 20
Mary Caroline Butterworth 16
An entry in 1841 Census, St. Giles, Middlesex lists a Thos. Forbes with mother, Louisa living at 109 Russet Street. Louisa is recorded as an Artist.
Maln B Bowley 40
George Whittaker 20
Mary Bently 22
Areballa Ordoyle 23
Louisa Forbes 28
Thos Forbes 10
Rosetta Gosford 23
Eliza Maley 28
Louisa B Bentley 1
Charles Bowser 28
An Maria Bowser 23
Charles Bowser 2
Sera Sainson 17
I am afraid no Christening record has been traced.