The tax statement lists all adults who are eligible for the Australian Government Rebate (AGR) on private health insurance and who have been on a policy during the relevant financial year. This may include former partners but not children who are listed as dependants on your policy.
What about dependants?
Children on your policy who are under 31 do not get their own tax statement because they cannot claim the AGR and are not subject to the income test.
However, a dependent child on your policy can use a copy of your tax statement if they need to complete the private health insurance policy detail section of their tax return.