The PRO (pink icon) and the FREE (blue icon) version of Stop Motion Studio can be shared with all family members.
Sharing the in-app purchase of the FREE version with family members:
If you are using an iPhone, iPad, or iPod:
Apple added support for sharing in-app purchases in iOS14 and up. If you have an older device, you won't be able to share in-app purchases.
https://www.apple.com/family-sharing/
If you are using an Android device:
At the moment, Android does not support sharing of in-app purchases.
https://support.google.com/googleplay/answer/7007852?hl=en
Please bear in mind, family sharing is a device feature, and Stop Motion Studio has no control over the process. Please contact the store provider (Apple, Google) for more information.