Keep receiving ical reminders on my yahoo account?

My dad got a new apple computer a year ago, and I have never used one before. I must have set the ical to remind me of important dates. Instead of staying on my dad's calendar, it has been forwarding reminders to me on my own computer in my inbox; additionally, it is messaging my dad's mail account. (I thought it would all just remain on the calendar and I was not forewarned of this.)