The article presents an apparent contradiction in the marriages of the city of Barcelona in the 19th and beginning of the 20th century. Using the dispensation documents of marriage between kin of the Archive of the Diocese of Barcelona we show an increase of endogamous marriages in the city of Barcelona. There is a significant increase during the second half of the 19th century, which slowed down at the beginning of the 20th century. This trend is particularly puzzling in a context of urbanization and industrialization. Itis not however an exception to the general trend in Europe. Other researches show the same pattern not only in Catholic countries, but also in Protestant ones. We analyse the causes of this matrimonial behaviour. We present also thereasons given by their protagonists as they appear in the matrimonial dispensations documents of the Catholic Church. Finally we describe the medical and biological discourse about dangers to health and the inheritance of certain diseases that consanguineous marriages can cause. Marriage is not disciplined only by the religious doctrine of the Catholic Church. New secular actors enter the formation of a moral discourse on the definition of a good marriage.
Keywords: Marriage – Endogamy – “Cousin Marriage” – Incest prohibitions – Social Classes – Urbanization – Modernisation – Natural inheritance – Morality