In case you purchased our PRO version right in the app via Google Play or Apple's App Store.
Apple: Yes. This is possible since Dec 2020. All devices must be part of Apple's Family Program. It might help to press the "restore in-app purchases" button on the screen where you can purchase a subscription or lifetime licence.
Google: Yes. All devices must use the same EASY peasy email registration.
Amazon: Not automatically. If you purchased the PRO version via the Amazon App Store, it is not possible for now. Please contact our support at support@wonderkind.de, so we can further assist you.