Why cant I add my own debit card onto my iPhone if I am on my partners apple family for the sharing of apple music.

Before I joined my partners apple family to use his apple music for no cost to me, I bought my own stuff with my own debit card on my iPhone. Now that I'm on his family, anytime I try to buy something it tries to charge his card and it won't even let me add mine. Same issue with setting up my daughters iPhone under my ID as the parent, she cannot do anything on her iPhone and all my pics are on her phone even though she's got her own apple ID. This is just ridiculous. Any help??