Mont. Code Ann. § 72-2-718

If a class gift in favor of "descendants", "issue", or "heirs of the body" does not specify the manner in which the property is to be distributed among the class members, the property is distributed among the class members who are living when the interest is to take effect in possession or enjoyment in such shares as they would receive under the applicable law of intestate succession if the designated ancestor had then died intestate owning the subject matter of the class gift.