The family ticket is valid for 1 or 2 adults and their own children (aged 6–17) with the same residential address. Exception: Grandparents and their own grandchildren (aged 6–17) may purchase a family ticket under these conditions.

Children's tickets are only valid when accompanied by an paying adult!
Children up to and including the age of 5 travel free when accompanied by a paying adult! 
An exception is made for children on ski courses, who require their own ticket (regardless of age).