The obligatory share in the structure of the constitutional and legal institution of inheritance is the main, universal, natural and inalienable element, it combines the signs of personal, social and economic human rights. The scientific hypotheses of this study are based on the provisions of modern constitutional and civil legislation, modern concepts of law: the mandatory share in the structure of the constitutional and legal institution of inheritance as an element of the legal status of the individual, related to the fundamental (fundamental) rights enshrined in the Constitution, forms the basis for regulating relations arising between subjects of the constitutional right of inheritance. The design of the study covers a comprehensive analysis of the theoretical, legal and practical problems of the considered legal category - the mandatory share in the structure of the constitutional and legal institution of inheritance - on the example of the Republic of Kazakhstan and the Republic of Uzbekistan.