« Reply #5 on: Monday 30 November 15 17:30 GMT (UK) »
The 1850s were a period of great emigration from Cornwall. I would consider the possibility that he left England for Australia, Canada or the United States as a young man before the 1861 census. With his mother remarried, he might have had more than average incentive to leave home.
re the 1855 death, in 1851 there were several John Harrys in St Germans reg dist, dobs c 1778, 1804, 1829, 1838, so it is perhaps more likely the 1855 death was one of them. (Looking for them in 1861 could rule them in or out ... on a quick search I don't see any of them.) But only the certificate might say for sure.
adding: For example, two John Harrys aged 28 arrived in New York from England in May and August 1869:
https://familysearch.org/ark:/61903/1:1:QVPV-WYHPhttps://familysearch.org/ark:/61903/1:1:QVPV-CC88... so if he did emigrate, he could be a bit of a needle in a haystack.
HILL, HOARE, BOND, SIBLY, Cornwall (Devon); DENNIS, PAGE, WHITBREAD, Essex; BARNARD, CASTLE, PONTON, Wiltshire; SANKEY, HORNE, YOUNG, Kent; COWDELL, Bermondsey; COOPER, SMITH, FALLOWELL, WILLEY, Notts; CAMPION, CARTER, CRADDOCK, KENNY, Northants; LITTLER, CORNER, Leicestershire; RUSHLAND, Lincolnshire; MORRISON, Ireland; COLLINS, ?; ... MONCK?