When a user RESTOREs a purchase on a device.
Is original purchase tied to a device, apple-id, family devices?
device - meaning he can restore on only 1 device.
apple-id - meaning he can restore on multiple devices based as long as the apple-id is the same as the original purchaser.
family - all "family" devices can restore the purchase.
In-app purchases are linked to an Apple ID. Non-consumable purchases and auto-renewing subscriptions should be available on all devices where that Apple ID is used and you must provide a restoration process (either automatic or manual, or both) to allow this.
Consumable purchases and non-renewing subscriptions do not have to be restorable. It is desireable that you provide some form of account where the user can log in to multiple devices, but it is not required.
In-app purchases are not shared via family sharing - See the Note under the “types of in-app Purchase” table