Convert patient to contact?

Hi,
Can i convert a patient into a contact?

Or maybe there is an alternate option for my situation:

I’m creating a new patient (born 2 months ago). I want to create a contact to whom I can send the invoice to. This is of course the mother or the father. I duplicate the patient (the baby), change the needed stuff, save and close this patient, add invoice address of the parent to the baby’s patient-data.

But then the parent is a patient, and not a contact. 😕