If you are seeing Birthday events on your calendar that are duplicates or that you don’t want to see, it’s likely a setting with your calendar provider is causing it.
For Google Calendar:
- Sign in to Google Calendar in your desktop browser
- Go to My Calendars > Settings > Birthdays
- Customise the birthdays you wish to see
- Sign into iCloud.com in your desktop browser
- Click on Calendar then tap the Settings cog icon on the bottom left
- Choose to tick or untick “Show Birthdays Calendar"