I need a larger family member count than currently provided to keep my kids safe.

I'm the dad of a family of seven (two adults, five kiddos) and need a larger family member count than currently provided.

Currently, Apple limits a family to six members). And we recently had to "kick out" our oldest son in order to add in my youngest. Obviously this isn't ideal. Firsty, cause we had to get that son his own AppleMusic account and he's had to repurchase apps we had as a family. But, more importantly, his mom and I can no longer use Apple's robust parental controls to govern his device—an iPhone that otherwise can't regular using services like OpenDNS or the controls in our mesh network.

What is the protocol for adding family members over six, total? I know many families with more than six parents and children for whom this is a burdensome issue.