California Code, Probate Code - PROB § 1811

(a) Subject to Sections 1813and 1813.1, the spouse, domestic partner, or an adult child, parent, brother, or sister of the proposed conservatee may nominate a conservator in the petition or at the hearing on the petition.

(b) Subject to Sections 1813and 1813.1, the spouse, domestic partner, or a parent of the proposed conservatee may nominate a conservator in a writing signed either before or after the petition is filed and that nomination remains effective notwithstanding the subsequent legal incapacity or death of the spouse, domestic partner, or parent.