In this article, author presents basic theoretical approaches in economy, sociology and demography, explaining the phenomenon of single-parenthood. In this paper, the following approaches are described: the theory of marriage (G. Becker), the transactional approach (R. Pollack), the family development theory and the family life cycle concept (E. Duval, R. Hill, P. Glikk), the theory of gender inequality (A. Cherlin) and the theory of the Second demographic transition (R. Lesteg, D. van de Kaa). Although such demographic events as the birth out of the marriage and divorce are the result of a conscious choice of the person, during long time they were considered by researchers as the events breaking normal sequence of stages of family development. The increase of nonmarital birth rate, the growth of the number of divorces and the widespread of cohabitations in the 1980th led to changes in matrimonial and reproductive behavior of people. These changes in behavior caused the revision of the existing approaches to the lonely parenthood, and the renewal of conceptual framework: the term “union” and “cohabitation” began be used together with the term “marriage”, and the term “life cycle” was replaced by the term “life course”.

Keywords: marriage market, Second Demographic transition, gender equality, family life course, single-parent family, single-parenthood, transactional cost approach