Your taxable household includes the primary tax filer, spouse, and any qualifying dependents. Even if they aren't getting insurance on your plan, be sure to mention your spouse and dependents as part of your taxable household when filling out the application.
Essentially, each dependent in your household decreases the amount of your income that gets taxed, which can help you save money on health insurance and taxes!
For clarification on how to classify a dependent, here's an example:
A child living with their parents while going to school would be considered a dependent and would be included in the taxable household. However once that child starts filing their own taxes independently, the parents would no longer claim them as a dependent and would not include them in the taxable household.