USA Today has written about the clear differences between biological and legal parentage:
The article shows the mess the law is in as to dealing with the advances in IVF and surrogacy- a position that is broadly reflected in Australia. Here lawmakers have struggled to make the laws reflect what is happening. For example, when I presented to NSW MP's in September abourt surrogacy matters, they were stunned that under their legislation "parents" of children born overseas via surrogacy (whether legal or illegal) may not be parents as a matter of law in NSW.
This is even if they are considered to be "parents" under the Australian Citizenship Act, or biologically the "parents" or even the "parents" in the overseas jurisdiction where the children were born.
Confused? Probably a good starting point for confusion is the Queensland couple who went to Thailand for surrogacy and then found themselves the subject of the Family Court surrogacy case, which I wrote about here: http://surrogacyandadoption.blogspot.com.au/2012/08/family-court-decides-international.html.