Population is of great significance in all spheres of social and economic life; the total number of population, natural population growth (natality and mortality) and its structure in various categories. Considering the marital status, the structure of population is one of the most important indicators of the composition of population, since it indicates the one of the most important factors of the reproduction of population. It specially refers to those countries which are like our country, since their greatest natality in most cases comes from legal marriages. The most complete structure of population, according to the marital status, comes from the registers, which are made during the considerable time intervals (10 years, most offen). Vital statistics also analyzes the natural movement of population, Knowing the marital status of the population, which (in)directly influences publishing the date of the number of those who got married and divorced, is not sufficient for the analyses of the population's development. Considering the complexity of the examined phenomenon - not being officially married - the use of complementary sources of data imposes itself as a fundamental principle. One necessarily needs to use the knowledge of various sciences and scientific disciplines. Besides sociology, demography, statistics, ethnology history, there will be also theological literature. The goal of this work is to find the other possible sources of data about the marital behaviour of the population: for we are the witnesses of the increased number of the informal relationships. Before they get married, it has almost become a sort of rule that a young couple "lives together", and only after that, they eventually get married or separate.