Perhaps distinguish between families and teams by features, instead of maximum user count, focusing on the thought that business desires “control”, but “sharing” is enough for families.
For example, family plans likely could get by with the only permission being manage-collection, with view and edit becoming restricted to business plans.
And, families can get by with owner and user roles, with admin and custom being limited to business plans.
Families also could be limited to 6 (or fewer) collections. Personally, I only have 3 - Parents, Adults, and Minors.