Under the Dutch healthcare insurance system, nearly everyone is required to take out insurance on an individual basis. It is likely that your family will not be insured on your own healthcare insurance policy. Be aware that you will have to find a suitable healthcare insurance solution for them so as to ensure they are covered for medical expenses.
Children up to the age of 18 years pay no premiums for public healthcare insurance. However, the parents are responsible for ensuring that their children have a public healthcare insurance policy.