You serve them with Petition .
Notice California law them allows for court to approve it and you can just distribute it to the heirs.You don't need to have signed document.You can proceed without the document .
11640. (a) When all debts have been paid or adequately provided for, or if the estate is insolvent, and the estate is in a condition to be closed, the personal representative shall file a petition for,and the court shall make, an order for final distribution of the estate. (b) The court shall hear and determine and resolve in the order all questions arising under Section 21135 (ademption by satisfaction)or Section 6409 (advancements). (c) If debts remain unpaid or not adequately provided for or if,for other reasons, the estate is not in a condition to be closed, the administration may continue for a reasonable time, subject to Chapter 1 (commencing with Section 12200) of Part 11 (time for closing estate).
11641. When an order settling a final account and for final distribution is entered, the personal representative may immediately distribute the property in the estate to the persons entitled to distribution, without further notice or proceedings.
11642. Any property acquired or discovered after the court order for final distribution is made shall be distributed in the following manner: (a) If the order disposes of the property, distribution shall be made in the manner provided in the order. The court may, in an appropriate case, require a supplemental account and make further instructions relating to the property. (b) If the order does not dispose of the property, distribution shall be made either (1) in the manner ordered by the court on a petition for instructions or (2) under Section 12252 (administration after discharge) if the personal representative has been discharged.