Other apple user is abel to see my family calendar

My brother created family group.

Afterwards i left this family group and created my own family group.

A year later my brother tells me he can still see my "Family calendar events" despite he is not in my family group and i am not in his family group.

I have checked all of iCloud options and Calendar share list and nowhere there is information that my calendar is being shared with anyone else but my girlfriend.

How can this be possible?

And how can i remove other people from my calendar if apple is NOT showing any other shared person?