Section 10-6.4. Exercise of a power of appointment; required consents

(a) When the consent of the donor or of a third person to the exercise
  of  a  power of appointment is required, such consent shall be expressed
  in a written instrument, subscribed  by  the  person  whose  consent  is
  required;  and to entitle the instrument of exercise to be recorded, the
  signatures  of  the  donee  and  of  the  person  consenting   must   be
  acknowledged  or proved in the manner required by the laws of this state
  for the recording of a deed of real property.
    (b) Unless the donor expressly provides otherwise:
    (1) When the consents of two or more  persons  are  required  for  the
  exercise of a power of appointment, all must consent.
    (2) If before the exercise of the power:
    (A)  One  or  more of such persons die, the consent of the survivor is
  sufficient.
    (B) One or more of such persons become incompetent, the consent of the
  competent person is sufficient.