California Code, Revenue and Taxation Code - RTC § 3952

The complaint may further include as defendants persons unknown to plaintiff who claim any right, interest, lien, or claim on the land or cloud upon the title of plaintiff thereto arising prior to the date of the tax deed.  In any case in which any person who appears to have had an interest in the land or any claim or cloud upon the title of the plaintiff thereto is known to be dead, the heirs and devisees of that person may be sued as “the heirs and devisees” of the person, naming him or her, or if the person is believed to be dead and that belief is alleged in the complaint on information and belief then the heirs and devisees of that person may also be sued as “the heirs and devisees” of that person, naming him or her, provided that the person is also named as a defendant.