John and Richard TONKIN emigrants to USA

[Wint]

Am looking for info on John Ford Tonkin born in Flushing in 1834 and his brother Richard William born 1837. Richard married in Chile in 1863. Both shown on 1851 census but believe they must have emigrated before the 1861 census.

Wint

[excel]

Where was he in 1851 and what was his occupation? Did he marry? The answers may help to narrow the search as there are quite a few John Tonkins in Cornwall born in the 1830's .
So far all I have found is the following:
John Tonkin 11 May 1853; ship: Baryne John, Plymouth to New York; b c 1830 Great Britain; Miner;
John Tonkin, 20 Aug 1859; ship:Henry Clay, Liverpool to New York; b c 1838, England; Tailor;  Liverpool to New York.
John Tonkin 5 Sept 1864 ship: City of Washington, Liverpool to New York; born c1833; origin, England; Labourer;

[Wint]

Both John and Richard were living at home in Mylor with their parents in 1851 and were listed as carpenters apprentices. John Ford Tonkin was listed as an engineer when back in England in 1881. Richard married in Copiapo Chile in 1863 which I believe is a mining area. John was married to Julia Thomas Richards I can't find a marriage record for them anywhere.