Hi

This is the birth for Lily May Suckling and her parents names John Phillip and Sarah Jane Millard.
http://linctas.ent.sirsidynix.net.au/client/en_AU/names/sear...
You can search here for information on her parents and possibley sibllings if they were born in 1899 and before.

Trove digitised newspapers has death/funeral notices for Lily's father John Philip and Sarah Jane which gives you the names of their children
http://trove.nla.gov.au/ndp/del/article/25858261?searchTerm=...
Is shows that Lily is now Mrs Sullivan and googling her name brings up this
http://gravesoftas.com.au/Cornelian%20Bay%20Live/Church%20Of... showing that she died 14th Nov 1980.

Joseph Clarke may prove a little more difficult as it is a common name.
Could you please give all info on the baptism certificate. Does it have parents ages middle names etc
Hope all this helps in the beginning of your search.

Karin