A more thorough explanation:

Term: Privy
Definition: A privy is a person who has a legal interest in a matter or property. There are six types of privies: (1) privies in blood, such as an heir and an ancestor; (2) privies in representation, such as an executor and a testator or an administrator and an intestate person; (3) privies in estate, such as grantor and grantee or lessor and lessee; (4) privies in respect to a contract — the parties to a contract; (5) privies in respect of estate and contract, such as a lessor and lessee where the lessee assigns an interest, but the contract between lessor and lessee continues because the lessor does not accept the assignee; and (6) privies in law, such as husband and wife. In a legal case, a privy can be someone who controls a lawsuit though not a party to it, someone whose interests are represented by a party to the lawsuit, or a successor in interest to anyone having a derivative claim. For example, if a person inherits a property from their grandfather, they become a privy in blood to their grandfather's estate. If a person's business partner is sued, the person may be a privy in respect to a contract. The examples illustrate how a person can become a privy and the different types of privies that exist.