iCloud Custom Domain, Family sharing - how many domains possible?

[bsmr]

Hi,

I do have a question concerning maximum own domains within iCloud Mail Family Sharing with own domains.

I know, there is a limit of 5 domains for my account. But what about my family members. Is it possible for them to add new domains by themselves? Or is it only possible for me as the ‘admin’? What can I do if I have more than 5 domains which I want to share?

Would be nice to get a feedback.

 

[bsmr]

No one who can help here? Apple support does not answer.