Q: Child's purchases coming off MY Gift Card!

Hello,

This has been very frustrating. I bought our children gift cards and they added them to their accounts. For some reason, when one of my children makes a purchase, it comes off of "my" gift card and not his. He is signed into "his" account and he's not part of our family sharing because our family is too large. I had him sign in and sign out multiple times and then we did a small in app purchase on his phone and it still came off of mine. He doesn't have a hand me down phone either, so it's not like it used to be my phone. His was new from the store. For some reason they think his purchases are mine!