I can only find one Richard in Goulburn area so given this ...
Notice.
RICHARD LAMB, who was some short time
since seen in Goulburn, is requested to
write to his Sister, ANN MARKS, of Binda.
January 3, 1856.
... and the location of Ann's marriage I'd say she was a sister of the convict although that would mean Richard was baptised in Warwickshire and Ann in London.
I think this is the right baptism ...
Richard b. 17 Feb 1816
Baptism Date: 11 Mar 1816 St Martin Birmingham, Warwickshire, England
Eleazer LAMB [Glass cutter] & Susanna
... so can't be the right baptism for Ann with different parents.
1913 NSW Electoral Roll - GOULBURN - MUMMELL POLLING-PLACE
LAMB Annie, Mummel, domestic duties
LAMB Eliezer, Mummel, grazier
plus others
Dave