There's a marriage John Martin and Mary Clarke 7th Apr 1822 in South Petherton too. 
The occupation labourer fits much better with this family than gent!
Death of son Noah
Noah Martin Age 41
Death Place Victoria
Registration Date 1866
Registration Place Australia
Father
John Mother
Mary Clarkhttps://www.findagrave.com/memorial/200876065/noah-martinMary Clark Baptism 7 Jun 1799 South Petherton, Somerset
Father
Noah Mother Mary
Could this be mother Mary's burial
Mary Martin Age 33
Burial 9 Sep
1831 South Petherton, Somerset
Not sure about this burial if daughter Elizabeth Martin born 1828
John Martin Age 34
Burial 1 Jul
1827 South Petherton, Somerset
images on Anc*y