well, the use of 'the younger' suggests that 'the older' was somewhere nearby and probably in the same parish. Otherwise, why
make the difference?
Possible for John senior
1841 Weeth, Camborne HO107/141/3 folio 5 pg 2
John Marks 60 copper miner
Elizabeth 60
Josiah 20 copper miner
All 3 have a Y in the column noting if born in county, but in the next box which is meant to show Scotland, Ireland or Foreign Parts, there is what looks like Norfolk on the line for Elizabeth.
Josiah's baptism is on the Cornwall opc site
http://www.cornwall-opc-database.org/search-database/more-info/?t=baptisms&id=1475851& there are several other baptisms to the couple, first one in 1802 and including this one of a Henry
http://www.cornwall-opc-database.org/search-database/more-info/?t=baptisms&id=16408851851 College St, Camborne HO107/1916 folio 13 pg 18-19
Henry Marks head mar 46 copper miner
Elizabeth wife 50
Henry son 22 copper miner
Joseph son 16 copper miner
James son 14 copper miner
William H 12 copper miner
Francis son 10
Susan dau 8
Thomas J son 5
Elizabeth mother widow 74 b. Norfolk, Lynn
John Bennetts lodger 16 copper miner
all born Camborne unless noted
The first marriage of your John looks to be to Catherine Villanoweth 1/10/1821
baptism for their son John
http://www.cornwall-opc-database.org/search-database/more-info/?t=baptisms&id=1476374Cornwall record office have some documents relating to Henry & family, & father John gives evidence on one. Search on this link for Henry Marks for the references
http://crocat.cornwall.gov.uk/dserve/dserve.exe?dsqApp=Archive&dsqDb=Catalog&dsqCmd=Search.tclYou can order copies on this link
http://www.cornwall.gov.uk/default.aspx?page=14713Hope something here helps.