California Code, Probate Code - PROB § 11952

(a) Notice of the hearing on the petition shall be given as provided in Section 1220 to the personal representative and to the persons entitled to distribution of the undivided interests.

(b) At the hearing the persons entitled to distribution of the undivided interests shall be considered the parties to the proceeding whether or not they have appeared or filed a responsive pleading.  No one shall be considered as a plaintiff or as a defendant.

(c) Any objection to the jurisdiction of the court shall be made and resolved in the manner prescribed in Part 19 (commencing with Section 850) of Division 2.