Who owns the Family Sharing purchases?
According to Apple:


  When you set up purchase sharing, one adult in the family—the family organizer—agrees to pay for any purchases that family members make while they're part of the family group. 
  
  After it's paid for, a purchased item is added to the account of the family member who made the purchase. If you turn off purchase sharing, each member keeps their purchases, even though they were paid for by the family organizer.


So while the Organizer is the one who agrees to pay for the app, the 'owner' of the app is the Apple ID who made the purchase.