Can sync calendars between iPhone and iPad but not contacts
my Wife and I each have an iPhone and an iPad. User name is the same for both iPads and one of the iPhones, and different for the other iPhone. Calendar items sync across all 4 devices. Contacts sync only across the 3 devices with the same user name. On all devices calendar and contacts are set to sync with iCloud. Why can we not sync calendars to the iPhone with the different user name, but can sync the calendars?