Cal. Prob. Code § 2106

(a) The court, in its discretion, may appoint one guardian or conservator for several wards or conservatees.
(b) The appointment of one guardian or conservator for several wards or conservatees may be requested in the initial petition filed in the proceeding or may be requested subsequently upon a petition filed in the same proceeding and noticed and heard with respect to the newly proposed ward or conservatee in the same manner as an initial petition for appointment of a guardian or conservator.