i am not shraing any apps with my family, and yet the owner of the fsmily plan is being charged for my app renewals. why is this and how can i stop it

Did the sharing organizer disable purchase sharing?

From Add a family member to your shared subscriptions - Apple Support

"If you're the family organizer and you don't want to pay for family members' purchases and subscriptions, you can turn off Purchase Sharing [ How to share apps and purchases with your family - Apple Support ]. When Purchase Sharing is turned off, everyone must use their own payment method. When Purchase Sharing is turned off, family members can share subscriptions, but they can't share individual purchases like apps or books."

Otherwise you need to add balance to your account using gift cards so that is charged first (still not a 100% guarantee since some things cannot be paid using account balance).