Duplication of events across shared calendars

Duplication of events across shared calendars

I have 3 calendars set-up -
  1. My Calendar
  2. School term dates and events
  3. Birthdays & Anniversaries
I shared these 3 calendars with my husband.  But when he views all three, the events I have placed in my calendar also show in the other two.  So, each event is appearing 3 times.

When I view the three calendars together the events only appear once, and if I de-select my calender the events are not shown at all.