How can I avoid the Family Organizer (my brother) from being charged for my individual purchases?

Hello Beetlebum78,

It sounds like you want to stop your organizers card from being billed when you make a purchase. You would have to have a balance on your iTunes account, according to the following article:

Family purchases and payments

After you set up your family, any time a family member initiates a new purchase it will be billed directly to your account, unless that family member has gift or store credit. First, their store credit will be used to pay the partial or total bill. The remainder will bill to the family organizer's card

Thank you for using Apple Support Communities, take care!