Thomas Brooks (1776-1851) appear to have come over from England with the Petworth Emigrants. They arrived at Grosse Ile on June 8, 1832. Thomas and his family were taken off the ship and kept there because he was a cabinetmaker and they needed him build coffins as people died from the cholera epidemic. Does Grosse Ile have any records regarding people who may have been employed there? The Canadian government must have fed and housed the family during their stay. They may even have paid Thomas Brooks some wages.
Olive Tree Answer: Jim, I'm wondering how you know that Thomas was "taken off the ship and kept there" to build coffins. Did you find some record of this? Or is this family lore? As for Grosse Ile, their surviving records are online, and you can follow the link found at Filling in the Gaps The records are the names of 33,026 immigrants whose names appear in surviving records of the Grosse-Île Quarantine Station between 1832 and 1937.
You might also want to check the various Emigrant Agent records that have survived such as the Records of James Allison or Anthony Hawke. The Hawke Papers, letterbooks of Chief Emigrant Agent Anthony B. Hawke are available at the Archives of Ontario from 1831 to 1892. You cannot search the Hawke records pre 1865 online, for those earlier years you must view the microfilm through the Archives of Ontario. Records of James Allison, Emigrant Agent at Montreal, 1823-1845 are searchable at Ancestry.com
If you are lucky you may find some brief notation for your ancestor in one of the Emigrant Agent papers.