vol. 18 núm. 24 (2016)

Introduction: Current analysis of the legal basis for the frequent de facto marriages and both the origin of these practices and their implications for the legal system supposes delving into a rather unknown area, bearing in mind that we are living in a time of possible crisis for the traditional family. Methodology: For this reason, we will investigate how the absence of basic assumptions—especially legal capacity, or conubium—inflenced extramarital relationships. We will also investigate what was, in short, the raison d’être of the prohibitions of the designation on the part of classical Rome of legitimate marriage as iustum matrimonium. Results: We defend six criteria for grouping together the large number of extramarital unions that followed, highlighting: concubinage; cohabitation; homosexuality; incestuous marriage, sham marriage, and marriage between absent parties; unions with parties who lacked the physical capacity for marriage; adultery; and prostitution.  Conclusions: We conclude with a brief mention of the ideological inflence of the emperors, Christianity, and regulations on intersexual and third gender relationships, recently approved in Europe