§ 631. Defendants. Where the complaint demands judgment for the
immediate possession of the property, if the property is actually
occupied, the occupant shall be made defendant in the action. If it is
not so occupied, the action shall be brought against some person
exercising acts of ownership thereupon, or claiming title thereto or an
interest therein, at the time of the commencement of the action. Any
person claiming title to, or the right to the possession of, the real
property sought to be recovered, as landlord, remainderman, reversioner,
or otherwise adversely to the plaintiff, may be joined as defendant.