N.Y. Est. Powers & Trusts Law § 10-6.4

§ 10-6.4 Exercise of a power of appointment; required consents\n (a) When the consent of the donor or of a third person to the exercise\nof a power of appointment is required, such consent shall be expressed\nin a written instrument, subscribed by the person whose consent is\nrequired; and to entitle the instrument of exercise to be recorded, the\nsignatures of the donee and of the person consenting must be\nacknowledged or proved in the manner required by the laws of this state\nfor the recording of a deed of real property.\n (b) Unless the donor expressly provides otherwise:\n (1) When the consents of two or more persons are required for the\nexercise of a power of appointment, all must consent.\n (2) If before the exercise of the power:\n (A) One or more of such persons die, the consent of the survivor is\nsufficient.\n (B) One or more of such persons become incompetent, the consent of the\ncompetent person is sufficient.\n