Hi there,
Following up from both Merlin's and Aussie1947's posts.
Here is a NSW journal's mention for the 1886 death of the 90 year old. He was late resident of NSW.
http://trove.nla.gov.au/ndp/del/article/71076986 8 May 1886 Australian Town and Country Journal
DEATHS. . ; ALGEO January 10, at The Grange, Gin Gin, the residence of his son,William Bntterfleld Algeo,aged 90, late resident of New South Wales
The NSW SRO online index for Insolvency has him as a Settler in 1843 at Parramatta (so definitely an adult)
http://www.records.nsw.gov.au/state-archives/ And it is likely he was a surgeon dentist as per this Trove cutting
http://trove.nla.gov.au/ndp/del/article/12927683 5 June 1851 SMH William Butterfield Algeo, late of Liverpool street, Sydney, surgeon-dentist, now of Darlinghurst Gaol, a pauper
The Qld dc should give you how long he had been in the colonies, particularly NSW (‘late resident of ...’), .I it seems likely it would be his son providing the information for that 1886 cert, so it should detail William’s marriage/s and children and may even include the names of William’s parents.
Perhaps the 90 year old, late resident of NSW, retired dentist had gone to his son at Gin Gin to be cared for there, perhaps “The Grange” was the name of the homestead/property held by the son.
Have you contacted the Bundaberg family history group? I feel sure they would have a good understanding of Gin Gin and its 19th Century pioneers.
http://bundygenies.110mb.com/ Cheers, JM