In a Apple ID and password on your device.
If a child is too young to create their own Apple ID, the organizer, a parent, or a guardian can add the child to the Family Sharing group and create an Apple ID for them.
Go to Settings > [your name] > Family Sharing.
Tap [your name], then tap Stop Using Family Sharing.
The organizer can disband a family group. When a Family Sharing group is disbanded, all members immediately lose access to the shared content and subscriptions.
Go to Settings Apple Support article: Leave Family Sharing