Welcome Roxie,
There's a similar thread here:
http://www.rootschat.com/forum/index.php?topic=740477.0There's strict regulations and guidelines in each of the states and territories of Australia that focus on providing for the expectation of privacy for the individual. In Australia a person's name is usually considered to be part of that expectation. It is sometimes referred to as 'sensitive' information. It is part of an individual's identity.
Depending on which state or territory your Nan's brother settled in, will affect how long the various restricted access regulations apply. Each state/territory has its own BDM system. Some states you will need to wait 30 years after a death before a death cert can be available to anyone who is not named on the registration. Some are more than 30 years, and some are less.
The How To thread on the Australia board
http://www.rootschat.com/forum/index.php?topic=368728.0 at reply #2 explains the Living Person policy, and has some tips and includes the following sentences
Although we fully understand you would like recent information to add to your tree, or that you may wish to make contact with birth families, relatives you lost contact with when they immigrated to Australia, missing family or friends, we are afraid we are unable to assist you. and
Although we are keen to help you make connections, there are times, however, when other community networks will be able to do more and this is especially so in the case of people searching for their birth parents/missing people. We suggest using Google Search will lead such searchers in the right direction.
We are sorry we are unable to help you with any searches for the living but may we wish you every success in your hunt 
Cheers, JM
