John and his wife share an iCloud account and whenever his wife makes a phone call, it appears on his phone and vice versa. Why is that? Leo says it's because they're sharing the same Apple ID. They will also be getting the same text messages as well. Leo recommends having separate iCloud accounts and Apple IDs. Then share the contacts, calendar and other data with a shared Google account. That way it won't impact their phone calls, text messages, etc. All they'll need to do is add that account in their phone's mail, contacts, and calendar settings. Or, one of them can turn off iCloud drive and it will no longer sync to it. But that means one of them won't be backing up to the cloud, either.
They can also turn on family sharing if they want to share contacts, calendars, and even music.