Can family members view or access my vault in LastPass Families?
Each person, regardless of their role in the LastPass Families account (i.e., Family Owner, Manager, or Member), can only access their own personal vault. This means that nobody has the ability to view or access another person's vault within the account (regardless if they are a Family Owner or Manager).
While you cannot share your whole vault with another person, you can use the Sharing Center to share individual items (passwords, payment cards, secure notes, etc.), or create a shared folder and fill it with items to share with another person within your LastPass Families account.