https://www.apple.com/legal/internet-services/itunes/us/terms.html
M. "Family Sharing Rules: You can only belong to one (1) Family at a time, and may join any Family no more than twice per year.
As for getting around the restriction you will have to ask Apple. The people in this community are just other customers like you, not official Apple Support.
This support page has information about contacting Apple support and service ➔ https://support.apple.com/106932 If live support options (chat and/or telephone) are available they will show near the bottom left.
- Telephone numbers may only work when calling from the same country.
- Chat options (telephone numbers appear as active links, not plain text) may depend upon cellular connectivity. If a number shows as an active link, click on it to see additional options.
- If chat is not available on the top level support page, try selecting your hardware and narrow down your issue to see if a support article offers a support link offering chat. For example, the contact support link on this page https://support.apple.com/119902#zerobalance offers a chat link about emptying account balance even on a computer where the top level page does not offer any chat.
With an iPhone, iPad, or Vision, you may be able to chat using the Apple Support App if it is available in your country —> https://apps.apple.com/app/apple-support/id1130498044