Jean, I'm guessing that from your subject heading (1840-1863) you haven't located Thomas John Hampton in the IOM 1841 and 1851 censuses. Now that you've given the names of his parents and siblings, I believe that this is his family listed below (Ancestry's transcriptions).

So in 1851, he was listed as John T Hampton, and he wasn't with his family in 1861. This narrows down the search period for his passage to Australia, and since it seems that he may have been the only one of his close family to travel, perhaps you should concentrate your search from 1854-1861. Also, he may have travelled as John Thomas Hampton.

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1841
German 1/7
Corvalla

Name Age
Thos Hampton 25
Elizabeth Hampton 20
Thos Hampton 1
Robert Hampton 1 MO

In same dwelling as John and Elizabeth Kaighin (Eliz Hampton's parents ?)

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1851
Michael 4/5

Name Age
Thomas Hampton 37
Elizabeth Hampton 35
John T Hampton 11
Robert Hampton 9
Jane Hampton 7
Catherine Hampton 5
Elizabeth Hampton 8
Isabella Halsall 15

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1861
Michael 4/2
Kerrow Glass Farm House

Name Age
Thomas Hampton 48
Elizabeth Hampton 45
Robert Hampton 19
Jane Hampton 17
Cathrine Hampton 15
William James Hampton 8
Samuel Hampton 6
Charles Alfred Hampton 8 MO

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Jean C