A family is defined in the dictionary as "a social unit consisting of people who are related by blood or law." There are many different definitions of family, some more specific then others; sociologists tend to use a more specific definition, which can vary according to the sociologist. There are different types of family; the more commonly known ones, such as nuclear and extended. Universal means that it is found in all societies around the world; the universal family means a certain type of family that is found all over the world. Since the definition of family can mean different things to different people, it is debatable to conclude if the family really is universal, but some sociologists try to answer this question by studying the ideals of family and making classifications for it.
First to argue in favor of universality within the family after studying a sample of 250 societies was George Peter Murdock who defined a family as a social group that share a household, co-operate economically and produces offspring, He added that the family includes adults of both sexes, and one or more children Stating that, to be a family, the unit must fulfill the four essential functions: socialization, economic, sexual gratification, and reproduction. According to Murdock, These roles are important for the family to carry out because if they do not, they will not be able to produce children who are successful members of society, and if no family fulfilled these functions, society would cease to exist. Evidence for this could be found within Kibbutzim where children from six months spent most of the day and all of the nights away from their parents in children houses, in addition their socialization and education is left to caretakers who tell them how to arrange their day and how to eat. Early kibbutzim gravitated toward that system for several reasons; they wanted to demolish the nuclear family structure in favor of the group, they wanted their children to grow up in a kibbutz system, to train for their future lives. Economically, raising children collectively made sense during the tough early days, however through the 1990s, virtually all kibbutzim had moved towards capitalism, most kibbutzim had already turned away from communal sleeping, which had largely to do with the women who grew up in the children's house and, having become mothers, refused to let their children experience that same system. Many view this situation as in favor of Murdock’s theory as the neglect of the nuclear family was one factor amongst many that lead to the downfall of the Kibbutz. Murdock accepts that other institutions could perhaps perform functions of a family, though argues that the sheer practicality of the nuclear family as a way of meeting the four needs explains why it is universal.
Other sociologists have criticized Murdock’s functionalist approach, such as Marxist and feminists. There have also been challenges to the thesis that the family is universal by a Kathleen Gough who studied the Nayar