John Hackett and Mary Christopher

I am researching information on John Hackett b. abt 1772 in Wales and d. abt 1820 in Irish Town, Clonmel, County Tipperary, Ireland and his wife, Mary Christopher also b. abt 1772 Wales and d. abt 1820 also in Irish Town, Clonmel, County Tipperary, Ireland.  Their son, Pierce Peter Hackett was born 2 Sep 1795 in Irish Town, Clonmel, County Tipperary, Ireland.  Apparently, local records were burned in a Parish fire so we have been unable to pursue the line further.  We are hoping there is a Hackett ancestor with a family Bible or other records about John and Mary's parents so we can verify their birth and death dates and continue further research.  According to other information we have, Pierce Peter had a brother also named John Hackett b. abt 1798 in Irish Town, Clonmel, County Tipperary, Ireland and d. abt 1850 in Clonmel, County Tipperary, Ireland.  Thanks,  Warren Hackett