The union libre or consensual union is one of the conjugal arrangements in the formation of families of procreation throughout generations in Mexico. This is particularly the case among women who are very young and have low education among other characteristics. An important increase of this type of union has been observed during the last two decades. This paper analyzes the continuity and most recent changes that the union libre presents among the younger generations in the country. The analysis is based on the case study of Tijuana, B.C. and its population of young adults (18–29 years old), particularly females. This is one of the most prosperous and open to social change social contexts in the country; situation that contributes to the economic independence between the sexes, especially among the youth. The study uses information from the Mexican Population Census of 2010 and the survey Encuesta Sobre Salud Reproductiva de los Adolescentes de B.C., 2006.