According to the census of 1907 for St-Pierre, he was the son of Fernand Guyomard and Adele Luze. He was born in Sydney in 1906 (per the census).
Fernand was born (Marie-Fernand-Charles Guyomard) in St-Pierre on 2 Sep 1887; and according to the 1892 census there, he was the son of Corentin Guyomard and Sylvie Guerguin. The records of St-Pierre say Fernand and Adele were married in St-Pierre on 5 Mar 1910 (after the birth of your Charles in 1906)
See René LeDu's tree at Geneanet (paste all into your browser):
http://gw.geneanet.org/reneledu?lang=en;pz=emile;nz=le+du;oc...Adele (Adele-Marie-Josèphe-Catherine) was born at St-Pierre on 27 Oct 1882; in the 1892 and 1897 censuses of St-Pierre, she is 10 then 15 years old and living with the family of Pierre (Peter) Walsh and Catherine Clinch (born Burin (probably Lawn), NL). She may be a child of Catherine by a first marriage. Adele died in St-Pierre on 30 Jan 1959.
Corentin Guyomard was born in Plouézec (Côtes d'Armor), FR on 11 Nov 1858, at 1AM, the son of Jean-Marie Corentin and Marie-Anne Mevel; he was a mariner and was named after one of his birth witnesses: Corentin Serviget and François LePollis. Correntin Guyomard married Sylvie Marie Guerguin, daughter of Charles-Guillaume and Emilie-Caroline Puyol, on 26 Nov 1885 at St-Pierre. Sylvie was born at St-Pierre on 10 Dec 1861.
That should at least get you back to France.