Family Plan Apple Music Charges

Family Sharing, while Purchase Sharing is on, will send the bill for all purchases from group members to the organizer. Not just iTunes Store music, also App Store apps, and other iTunes Store purchases.

Family purchases and payments - Apple Support

Share App Store, iTunes Store, and Apple Books purchases with Family Sharing - Apple Support

• Note that sharing Apple Music Family itself doesn’t require Purchase Sharing. Those are separate switches, that can be turned on and off independently.
• Note that buying music from the iTunes Store is not included in the Apple Music subscription. Those are two separate ways to get music that should not be confused. Searching within the Music app lists music without prices. Searching music within the iTunes Store app list music with prices.