Shared Purchasing
Can I share my purchases and not allow family to purchase using my billing information?
iPhone 12 Pro Max, iOS 15
Question marked as
No, you can't. If you are the family organizer, you are responsible for paying for family members purchases as stated in the Related Article above.
"One adult in the family — the family organizer — pays for everyone's purchases. You can share apps, music, books, and more".