I agree with CatOne, checking the IGI both James and Francis Chamberlain (living with the Harts and Thurza on the 1851 entry) and others, all have the same parents listed as the Mary Elizabeth Chamberlain, christened 10th October, 1818, Great Bentley. User Submitted entries are often suspect but since all of these children have christening dates it would certainly make sense for you to view the film of the Parish Register for yourself.
It did make me wonder whether Mary Hart could be Mary Chamberlain having remarried.
Mary