Mont. Code Ann. § 19-2-802

19-2-802 . Effect of no designation of beneficiary or no surviving statutory or designated beneficiary. (1) If a member or payment recipient fails to name a designated beneficiary or if a statutory or designated beneficiary does not survive the member or payment recipient, the estate of the member or payment recipient is entitled to any accrued lump-sum payment or accrued retirement benefit not received prior to the member's or payment recipient's death. If the estate, as either a designated beneficiary or as a beneficiary by default as provided in this subsection, would not be probated but for the amount due to the estate from the retirement system, all of the amount due to the estate must be paid directly, without probate, to the surviving next of kin of the deceased or the guardians of the survivor's estate, share and share alike.

(2) Payment must be made in the same order in which the following groups are listed:

(a) husband or wife;

(b) children;

(c) father and mother;

(d) grandchildren;

(e) brothers and sisters; or

(f) nieces and nephews.

(3) A payment may not be made to a person included in any of the groups listed in subsection (2) if at the date of payment there is a living person in any of the groups preceding the group of which the person is a member, as listed. Payment must be made upon receipt from the person of an affidavit, upon a form supplied by the board, that there are no living individuals in the groups preceding the group of which the person is a member and that the estate of the deceased will not be probated.

(4) The payment must be in full and complete discharge and acquittance of the board and system on account of the member's or payment recipient's death.