Cal. PROB § 3111

(a) Except as provided in subdivision (b), any of the following persons may file, or join in, a petition under this chapter: (1) Either spouse, whether or not the spouse has legal capacity. (2) The conservator of either spouse. (b) If the petition requests approval of a proposed transaction, at least one of the petitioners shall be either a conservator or a spouse having legal capacity for the transaction.