I recently got married and my wife has a 8 yr old son that i'd like to adopt in nsw.

the bio father is not on the birth cert so therefore my wife put father unknown as he said it hasn't his and claimed she cheated on him and he refused to go on the cert.
He hasn't been in the childs life for over three years and we don't know where he is we have had child services look for him to see if he wanted access and they can't find him as he keeps moving from state to state.

How would i go about adopting my step son as we can't get the fathers permission?