Yup, that's doable. The CBSubs Family Plans integration provides that. They can invite users to join a plan. They can fully manage whom they invited as well (e.g. revoke someone's subscription). You can limit how many they can invite by a hard limit or per-user limit using a field. Feel free to give it a try on our demo site below as we provide a full access demo.
demo.cbdemosites.com/