Thanks for your question Stacie. The short answer is no; only one person is appointed to each position in the Australian Government.
However, it is possible to have someone acting in a position. For example, when the Prime Minister travels overseas to represent Australia or is on holidays, the Deputy Prime Minister performs the role of Acting Prime Minister.
There may also be someone appointed to assist a minister in performing their role in the government. For example, the Assistant Treasurer helps the Treasurer to do their job.