A mother leaves after her child is born and the father has raised the child for the child's entire life (6 years). It turns out that he is not the biological father. Does the real biological mother or father have any legal claim to the child if they come back 6 years later, despite the fact that the man who has raised the child for 6 years is on the birth certificate as the child’s father? This case is based in NSW, Australia so would be helpful in relation to Australian family law, please.