Another family sharing can't see apps question

There are three people in the family to talk about. All shared the same applieID (A) and bought apps.

AppleID A setup family sharing with the other accounts.

AppleID B is a child. Is logged into icloud with B and App Store as B. If go to iCloud Family then B family purchases is set to B. Everything works for B.

AppleID C is an adult. Is logged into iCloud with C and App Store as C. If go to iCloud Family then C family purchases is set to A. C cannot see any of the apps previously purchased. If C tries to change the Family Purchases to A they get a PPP up warning that sads all family members will lose access to purchases shared with A and can't change it for another 90 days.

how in the world can C get access to the apps like A and B?

thanks!