Q: Can we use our own credit card even though we belong to one family group?

Hello Trisa295,

Family sharing payments are all managed by the Organizer, and only the billing information on that account can be used to pay for an iTunes purchase. Take a look at this info from the following article:

Family purchases and payments

With Family Sharing, one adult in the family—the family organizer—agrees to pay for any iTunes, iBooks, and App Store purchases that other family members initiate while they're part of the family group. This also includes ongoing subscription purchases initiated by family members, such as iCloud storage, iTunes Match, and Newsstand subscriptions.

If the members of the Family have credits or have iTunes Gift cards redeemed, that balance gets used first so an option you all have is to apply iTunes credit in some way to these member accounts:

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.

Cheers,

Sterling