I noticed in the iOS FAQ (https://support.1password.com/pro-features-faq/) that the Pro features of the iOS app cannot be shared via Family Sharing because Apple does not support sharing in-app purchases with family members, but it sounds like AgileBits would allow family sharing if Apple supported it.
Can I suggest offering a paid version of the app since paid apps CAN be shared via Family Sharing? "Tiny Scanner" is an example of an app that offers the same "pro" features both through an in-app purchase and through an up-front paid version of the app.
1Password Version: Not Provided
Extension Version: Not Provided
OS Version: Not Provided
Sync Type: Not Provided