Hi there Millie1004,
It sounds like you are getting new eventst that are being created on your computer to your phone becuase they both have the same Apple ID signed in. If you want you can hide that calendar so it doesn't show the new events by tapping Calendars at the bottom of the calendar screen:
Calendar at a glance - iPhone
If that is a calendar you use, or you just don't want to hide it, your son can create a calendar for him to use on your computer, and you can hide that one on your phone when it syncs:
Choose File > New Calendar, then choose an account for the calendar.
Name the calendar and press Return.
Add or delete calendars - Calendar Help
Thank you for using Apple Support Communities.
Cheers,
Sterling