The graph above from Living in Australia shows how median household net worth changed between 2002 and 2006 for different age groups.
Couples have higher net worth growth than singles because typically single people live alone. Having children seems to have an effect on net worth. This may be because those who have children tend to buy larger houses and property prices in Australia have risen greatly recently, compensating those who buy more real estate.
Looking at household net worth I don't think is very useful as a measure of wealth. For example, if you are a young adult living with your parents, your household net worth may be high because your parents own the house plus they may have high income. But they won't necessary share this wealth with you or they may share only a small portion of it with you. What is important is wealth under your own personal control.
Below is a similar chart for Americans.