I need to delete someone from sharing my calendar (ical)

To stop sharing an iCloud Calendar, see the following from: Share iCloud calendars on Mac - Apple Support

Stop sharing a calendar

In the Calendar app  on your Mac, do any of the following:

• Stop sharing your calendar with specific people: Place the pointer over the calendar’s name in the calendar list, then click the Share Calendar button . Click a person’s name, then press Delete.
• Stop sharing your calendar with everyone: Control-click the calendar in the calendar list, then choose Stop Sharing.
• Stop subscribing to someone else’s calendar: Control-click the calendar in the calendar list, then choose Unsubscribe.

If you don’t see the calendar list on the left, choose View > Show Calendar List.