When the customer is a minor/child and and you want to appoint a guardian for them, you need to create two customers in Tehden. First, create the guardian, and then the child as a separate customer. When creating a child as a customer, add guardian's customer_id to child's parentcustomer_id-parameter.
company_customer/createTehdenCustomer Create both customers, first the guardian and then the child.
Screenshots from the user interface are in Finnish because a large part of our customers use Tehden in Finnish.