There has been paradigm shift from extended to nuclear family, rise in divorce incidences, decline in nuptial, and the emergence of new types of relationships. They include non-marriage cohabitation, decline in fertility rates, dynamic gender, living together separately, and cross-generational relations during the twentieth century. Households of single-motherhood, single pensioners, and unemployed couples with children continue to experience unequal distribution of income. These social changes in existing family structures have been aggravated by the economic, technological, and cultural factors. Families have been under duress due to increasing population, globalization, industrialization, urbanization, and changes in gender roles. The changes in existing family features have had demographic as well as social impacts. Diversity of households does not involve family decline. Notwithstanding the reduction in the number of traditional family households, opportunities for single-person households and cohabitation have been increasing. In spite of the improvement of income of poorest families in Britain, the overall inequality in wealth distribution was higher in the mid-1990s compared to any other post-war period. This paper will present a discussion of sociology and family. Part 1 of the paper will address the changes and variety of family structures in the 20th century with reference to Marxist, Functionalist, and Feminist Theories of social changes. Part 2 of the paper will present an argument whether family is under threat in the 21st century. The analysis of causes and consequences of marital dissolution with reference to differences in status/culture and changing gender roles will form the basis of the argument. Part 1 1.1. Variations in the family structure Family structures differ from one society to another. The nuclear family is the smallest family unit and is made up of husband, wife, and immature offspring. The vertical and horizontal extension of nuclear family results in an extended family. Feminists and Marxists have highly criticized the traditional family structure. Their perspectives have tended to underline the adverse effects of family life on women. According to feminist theory, family is regarded as an institution that encompasses power relationships rather than institution based on collaboration, love, and mutual interests. Men tend to gain more from family life than women do. Marxists theory supports feminist argument although they based their arguments on correlation between family and capitalism rather than the impacts of family life on women (Haralambos & Holborn 2004). Marxist feminists use Marxist theory although they view exploitation of women as a key phenomenon of family life. The functionalist perspective underscores the necessity for integration and harmony between the different sections of the society. A social system would be efficient if the parts of the system appropriately fit rather than abrade. The parts of the social system would be related functionally if they play a role in the integration and harmonization of the social system. Haralambos and Holborn (2004) observed that isolated nuclear family is suitable to meet the demands of the economic system. The isolated nuclear family appropriately meets the demands of geographical movement of workforce. 2.1.