So your application is really to remove the biological father's parental responsibility, and secondly to provide that the step-father has parental responsibility.
If you do not remove the biological father's parental responsibility, you will still need need to make decisions with him jointly - see s65DAC. This means he could still withhold his signature from documents such as passport applications.
You would have to set out compelling reasons to remove the biological father's parental responsibility. Usually it is removed in cases of child abuse (including domestic violence on the mother) or where the child expresses a desire not to want to have a relationship with the father. It is not usually otherwise removed.
If you are having a crack at this yourself you probably want to read some cases to get an idea of how judges think about these ideas.
Such as:
Kozar [2013] FCCA 339
DOHERTY [2014] FamCAFC 20
Ultimately though what you are seeking is difficult and you will need a persuasive argument.
If you do not remove the biological father's parental responsibility, you will still need need to make decisions with him jointly - see s65DAC. This means he could still withhold his signature from documents such as passport applications.
You would have to set out compelling reasons to remove the biological father's parental responsibility. Usually it is removed in cases of child abuse (including domestic violence on the mother) or where the child expresses a desire not to want to have a relationship with the father. It is not usually otherwise removed.
If you are having a crack at this yourself you probably want to read some cases to get an idea of how judges think about these ideas.
Such as:
Kozar [2013] FCCA 339
DOHERTY [2014] FamCAFC 20
Ultimately though what you are seeking is difficult and you will need a persuasive argument.