Hi iOSboy13,
Thank you for contributing to the Apple Support Communities.
It seems like you're trying to buy an app with iTunes Store credit but you're being asked for the family organizer's credit card information.
The family organizer may need to update or verify the billing information on their iTunes Store account, since Family Sharing requires a valid payment method on file.
You can ask the family organizer to verify or update their billing information using the steps in Change or remove your Apple ID payment information.
If they already have a valid credit card on file, they may just need to verify the information by re-entering the credit card security code.
Once they've done this, try buying the app again using the iOS device with your iTunes Store account and store credit.
If you still get the same message, I'd recommend contacting iTunes Store Support for more help. Just visit iTunes - Contact Us.
Cheers.