Q: Duplicate calendars on my iPhone

For the issue of duplicate calendars -- Get help with duplicate calendars or events on your iCloud calendar - Apple Support

For sharing an iCloud calendar -- iCloud: Share a calendar with others

Have you tried such things as logging out of iCloud on the device, turning off/on the device, reseting the device (simultaneously pressing home and on/off switch)?

Jonathan Lyons wrote:

 

The article you linked to was the one I read. It only explains duplicate calendars on OSX.  My "family" calendar only appears once on OSX.

 

For iOS, my iPhone, under iCloud, I have 2 "family" calendars.  It only suggests refreshing, which doesn't help.

Instead of refreshing try to uncheck calendar you do not need on the same page. It will not delete it, just take it out of the view. It would be great if you could eliminate the problem that brought it in the view, but the fact that they are not syncing and that problem is what you wanted to do next. So start easy, just uncheck from view.