Mont. Code § 72-2-721
If an applicable statute or a governing instrument calls for a present or future distribution to or creates a present or future interest in a designated individual's "heirs", "heirs at law", "next of kin", "relatives", or "family" or language of similar import, the property passes to those persons, including the state, and in such shares as would succeed to the designated individual's intestate estate under the intestate succession law of the designated individual's domicile in effect at the time the disposition is to take effect in possession or enjoyment as if the designated individual died at that time. If the designated individual's surviving spouse is living but is remarried at the time the disposition is to take effect in possession or enjoyment, the surviving spouse is not an heir of the designated individual.
§ 72-2-721, MCA