The Primary parent/guardian questions section is displayed on the question setup form by default. You can add a Secondary parent/guardian questions section, which will show exactly the same questions as the Primary parent/guardian on the online registration form.
You can't edit the Secondary parent/guardian, but you can delete it.
First name, Last name, Date of birth, and Gender are required questions for both sections. Answers to these questions are recorded to the person profile. Any other questions, if you make them as required for the Primary parent/guardian, don't become required questions for the Secondary parent/guardian.
If you create custom questions and group them as secondary parent questions, answers to these questions aren't recorded to the person profile.