Franck Roumy, The Birth of the Notion of consanguinitas in Medieval Canon Law and its Reception in Civil Law

In medieval roman-canon law, the term hereditas kept its meaning of patrimony and the succession of property rights, without any link to the modern idea of natural heredity. The latter can, however, be found in the concept of consanguinitas. In Roman law, this term referred to succession rights between close relations united by agnation. However, in canon law, from the 8th century on, it came to mean ‘blood’ kinship prohibiting marriage. Contracted through the ‘prolongation of the flesh’, as canonists worded it from the 12th century on, consanguinity creates lineages based on a community of blood originating from the unitas carnis of Christian marriage. As early as the second half of the 12th century, civil lawyers borrowed this new meaning of the term consanguinitas from the canonists. In law, it continued to have this meaning together with its original Roman sense until the end of the Middle Ages.