Montana Title 42. Adoption § 42-5-202. Effect of decree

(a) the relationship of parent and child and all the rights, duties, and other legal consequences of the relation of parent and child exist between the adoptee and the adoptive parent and the kindred of the adoptive parent;

(b) the former parents and the kindred of the former parents of the adoptee, unless they are the adoptive parents or the spouse of an adoptive parent, are relieved of all parental responsibilities for the adoptee and have no rights over the adoptee except for a former parent's duty to pay arrearages for child support.