If they were in Eretz Israel during World War I, they may have been
expelled by the Turks. Below is a link to a partial list of those who
were expelled to Alexandria. A number of those in the list have
Australia as their destination. Try searching by the various names in
your family way back when.
Maybe you will be lucky and find a trace of them.

http://www.isragen.org.il/siteFiles/1/153/4973.asp

Rose Feldman
IGS Webmistress