Demographic security in the form of achieving a demographic optimum is jeopardized by the barriers that arise as a result of ongoing social and economic transformations. The transformation of the institution of the family, which is a natural process of social modernization caused by the reduction of social control over the demographic behavior of the population, the increase in the status of women in society and gender equality, as well as the liberalization of behavioral norms and values, plays a leading role among them. The socio-demographic transformation of the family is interpreted from different positions, based on a variety of sociological, economic, and demographic theories. The modern concept of the family is increasingly moving away from the Soviet definition of "the unit of society". The aim of the article is to analyze the transformation of the Belarusian family through changes in its functions, type’s structure, and values. Over half a century, the Belarusian family has undergone fundamental changes: from patriarchal, multigenerational, large family to equal, egalitarian, nuclear, single-child family. The article highlights the main stages of changes in the structure of the Belarusian family in connection with the trends of demographic development of the society. At different stages, the stability of the family institution was influenced by various social structures. Today, the role of state institutions, which allow the family to expand its functionality, has significantly increased. However, the weakening of the function of caring for offspring as a fundamental factor in preserving the institution of the family, as well as the decline in the population's need for children, is a cause for concern.