I gave you Elizabeth's marriage, her father's name is on there, John, a miner. Samuel Hosking, like his father, was a blacksmith, again on the marriage record, and he is shows as a pauper on the 1851 census, so I think marrying beneath herself is a bit strong. Where are you getting this info from? You'd be better off looking at contemporary records.
This is a transcription of Samuel's baptism
http://www.cornwall-opc-database.org/search-database/more-info/?t=baptisms&id=1331401You can access a scan of some original records here
https://www.familysearch.org/search/collection/show#uri=http://www.familysearch.org/searchapi/search/collection/1769414Sam's baptism in St Hilary, abode noted as Goldsithney in the parish of Perranuthnoe
https://familysearch.org/pal:/MM9.3.1/TH-266-13194-128313-80?cc=1769414&wc=MMVH-V2K:n405888829John was not a master builder, he shows up on the census as a mine carpenter
1861 Goldsithney RG9/15941 folio 87 pg 23
John Oliver head mar 38 mine carpenter & sawyer b. Newlyn East
Elizabeth wife 42 b. Ludgvan
William Hosking son-in-law 18 copper, tin & lead miner b. Perranuthnoe
John Hosking son-in-law 14 copper, tin & lead miner b. Devonshire, Ashburton
John Oliver son 10 b. Newlyn East
James Oliver son 7 b. Newlyn East
son-in-law was used at that time as we would now use step-son
Hosking family in 1851
Great Bridge, Ashburton HO107/1871 folio 331 pg 36
Samuel Hosking head mar 36 (pauper) blacksmith b. Cornwall, St Perran
Elizabeth wife 34 b. Ludgvan
Samuel son 13 b. Ludgvan
Elizabeth Ann dau 11 b. St Perran
Mary dau 10 b. St Hillary
William son 8 b. Devon, Ashburton
John son 4 b. Ashburton
The baptism you have for Elizabeth is too early. I haven't checked relationships, but you need to remember that Hosking is a very common name in the area, and the mother wouldn't have married her brother-in-law, it was illegal and didn't become legal until 1905 or thereabouts.
Marriage for Samuel Hosking & Ann Bawden
http://www.cornwall-opc-database.org/search-database/more-info/?t=marriages&id=553001Pretty sure I didn't mention a marriage in Breage for William & Ann. I suspect it is this one
http://www.cornwall-opc-database.org/search-database/more-info/?t=marriages&id=343903The register entry giving William as junior suggests his father was called William as well. Also, the register shows William as a tinner.
https://familysearch.org/pal:/MM9.3.1/TH-267-11093-96647-81?cc=1769414&wc=MMVH-VQF:n484473889Hope some of this helps.