Cal. Probate Code § 11604

(a) This section applies where distribution is to be made to any of the following persons: (1) The transferee of a beneficiary. (2) Any person other than a beneficiary under an agreement, request, or instructions of a beneficiary or the attorney in fact of a beneficiary. (b) The court on its own motion, or on motion of the personal representative or other interested person or of the public administrator, may inquire into the circumstances surrounding the execution of, and the consideration for, the transfer, agreement, request, or instructions, and the amount of any fees, charges, or consideration paid or agreed to be paid by the beneficiary. (c) The court may refuse to order distribution, or may order distribution on any terms that the court deems just and equitable, if the court finds either of the following: (1) The fees, charges, or consideration paid or agreed to be paid by a beneficiary are grossly unreasonable. (2) The transfer, agreement, request, or instructions were obtained by duress, fraud, or undue influence. (d) Notice of the hearing on the motion shall be served on the beneficiary and on the persons described in subdivision (a) at least 15 days before the hearing in the manner provided in Section 415.10 or 415.30 of the Code of Civil Procedure.