Hi Jess,
Have you searched the BDM Registry for Victoria? Their online indexes seem to be broken at the moment so I cannot check. I see from your tree that his parents married in 1920 - if he was born after 1924 then that record will not be publically available as there are privacy restrictions.
He may have been a little younger than is recorded on his death cert, it depends on who the informant was and how well they knew him.
Debra