Apple iCloud+ own Domain for families – how many domains in total?

thinking about switching my domains to Apple iCloud+ Domains. Overall it's easy and nice, but I do have a question concerning number of maximum own domains I can connect to.

I know they're talking about a limit of 5 domains. What happens when a family member also adds another domains? Does every family member have 5 domains, or is it a maximum of 5 domains in one family? My father is a family member, but doesn't need the other family domains - he has it's own domains.

Can he stay within our family, but connect his own domains?

Best