When a member of my family goes to a new doctor they fill out forms that lays out who is responsible for the medical bills for each patient. the form does ask for insurance information, but also who cover the co-payment, co-insurance, deductibles, and uncovered expenses. They also ask us to provide an annual update for this information.
The answer will be what you told the doctor when you contacted for those services. They will send a bill the the responsible party. If you don't want to be responsible for those expenses that won't be reimbursed by the insurance company you must notify the doctors office prior to the service being performed.