How do I stop Family Member from making Purchases?

If you're the family organiser and want family members to pay for purchases themselves, turn off purchase sharing.

You can access your Purchase Sharing settings in Settings on your iPhone or iPad or System Settings on your Mac.

Turn off purchase sharing:

On your iPhone or iPad, tap Stop Purchase Sharing.

On your Mac, click Turn Off, then click Stop Purchase Sharing.

When purchase sharing is turned off, you'll stop sharing your purchases and lose access to the purchases made by your other family members. You can continue to share subscriptions like Apple TV+ and Apple Music, but everyone must use their payment method for purchases.

Source: How to share apps and purchases with your family – Apple Support

Child --> Approve what kids buy with Ask to Buy

Go to your Purchase Sharing settings in Settings on your iPhone or iPad or in System Settings. Turn off purchase sharing:.

How to share apps and purchases with your family

When you set up purchase sharing, everyone in the group gets immediate access to the songs, albums, movies, TV shows, books and apps purchased by family members ...

Family Sharing

To turn off App Store purchases for one family member while allowing all other members to use purchase sharing, you can remove them from the family sharing on your iPhone. Leave or remove a member from a Family Sharing group ...