How family sharing actually works
Each family member signs up for their own PassCryp account with their own master password. The plan owner creates a shared 'Family' vault and invites members. Each invitee's public key wraps a copy of the vault key, and from then on shared items are visible to everyone in the family vault.
Personal vaults stay personal: only the owner has the master password, only the owner can decrypt the personal vault key. Parents do not see kids' personal vaults; partners do not see each other's personal vaults. The shared vault is the only thing visible to all members.