Cal. CCP § 373.5

If under the terms of a written instrument, or otherwise, a person or persons of a designated class who are not ascertained or who are not in being, or a person or persons who are unknown, may be or may become legally or equitably interested in any property, real or personal, the court in which any action, petition or proceeding of any kind relative to or affecting the property is pending, may, upon the representation of any party thereto, or of any person interested, appoint a suitable person to appear and act therein as guardian ad litem of the person or persons not ascertained, not in being, or who are unknown; and the judgment, order or decree in the proceedings, made after the appointment, shall be conclusive upon all persons for whom the guardian ad litem was appointed.

The guardian ad litem shall have power, with the approval of the court in which the action, petition or proceeding is pending, to compromise the same, to agree to the order or judgment to be entered therein for or against the persons for whom the guardian ad litem was appointed, and to satisfy any judgment or order in favor of the persons, or release, or discharge any claim of the persons pursuant to the compromise. The court shall have the same power with respect to the money or other property to be paid or delivered under such order or judgment as is provided in Section 372 of this code.

The reasonable expenses of the guardian ad litem, including compensation and counsel fees, shall be determined by the court and paid as it may order, either out of the property or by plaintiff or petitioner. If the expenses are to be paid by the plaintiff or petitioner, execution therefor may issue in the name of the guardian ad litem.