My wife and I have separate iCloud accounts. We can share most every Apple productivity app (calendar, photos, email) and have them sync dynamically except for Contacts.
I understand how to add my wife’s iCloud account to Internet Accounts on my Mac and enable Contacts. However, I have to manually copy contacts from my iCloud account to her’s. I really want to have a dynamic sync such that a change in contact made on any of our five Apple devices will automatically change on the other four, just like Calendar does.