Which calendar service are you and your wife using? The Google calendar, Outlook, Yahoo? Also,are both of you using the same service, or is one using one and the other using a different one?
If this is a matter where both of you are trying to sync to a common Google Calendar, if you start up the Calendar app, when you look in the hamburger icon in the upper left (three horizontal lines), is the proper calendars (i.e. Events, Reminders, Birthdays, etc.) checked or unchecked?