What happens if my legal guardian doesn’t fulfill their obligations?

The Court has the power to remove a parental guardian where that parental guardian is unwilling to perform or exercise the duties, powers, rights and responsibilities required (or where the parent is for a grave reason unfit to be a guardian of the child), where doing so will serve the welfare and best interests of the child.
 
There are also some other ways that your legal guardians obligations can end: 

• when you turn 18 years old
• if you get married or enter into a civil union
• if you live with another person as your de facto partner (but this only applies in certain situations*)

 
* A quick note about de facto partners: 
The Interpretation Act 1999 sets out that a de facto relationship exists between two people where the two people live together as a couple in a relationship in the nature of a marriage or civil union (and are not married or in a civil union) and are both aged 16 or older.  For the purposes of the Care of Children Act specifically, a de facto relationship is not recognised for a person aged 16 or 17 unless the consent of a Family Court Judge has been obtained.