I already had the death and marriage certificates for William.
His death certificate showed he died 4 September 1888 at Narrigal in the District of Talbot and Amherst in the Colony of Victoria, and he was buried 7 September 1888 at the Majorca Cemetery.
His marriage certificate showed he married Mary Gill on 3 August 1858 at Amherst in the Colony of Victoria. William was a bachelor, age 29, birthplace Plymouth, England, profession miner, residence Emu, parents William Reeves, labourer, and Maria Crook.
I had found a baptism entry for him in the Devonshire baptisms on FindMyPast, but this was just a transcription, so I decided to see if there was an image available online anywhere. Since I had already looked on FindMyPast and Ancestry, the next site to try was FamilySearch.
I found an entry for him in the England, Devon Bishop’s Transcripts 1558-1887 collection, and there was an image available with the options to Sign In to FamilySearch.org, Access the site at a family history center, or Access the site at a FamilySearch affiliate library. I chose to sign in to FamilySearch, to view his baptism record.
The baptism record showed that William John, son of William and Maria Reeves, was born 4 July and baptized 24 August at East Stonehouse, Devon, England. His father was a Private in the Royal Marines, and their abode was Stonehouse.
I had already found William’s immigration record (he came to Australia on the “Emma Eugenia”, arriving in New South Wales in June 1849), and his family on the 1841 census (they were living in Shepton Mallet, Somerset). At this stage, I haven’t been able to find any other records for William.
Sources of information
 Victoria Registry of Births, Deaths and Marriages, death certificate 11591 (1888), William John Reeves; Registry of Births, Deaths and Marriages, Melbourne.
. Victoria, Australia Registry of Births, Deaths and Marriages, marriage certificate 2478 (1858), Reeves-Gill; Registry of Births, Deaths and Marriages, Melbourne
. FamilySearch, “England, Devon Bishop’s Transcripts, 1558-1887,” database and images, FamilySearch (https://www.familysearch.org/ : accessed 8 Sep 2017); baptism record for William John Reeves, East Stonehouse, Devon, England, https://familysearch.org/ark:/61903/1:1:Q2M3-SBFW; citing Baptism, The Devon Record Office, Exeter.