Starting from the Descriptio Mancipiorum Ecclesiae Massiliensis, an ordered list of some properties of the Church of Marseille in thirteen localities in the actual Provence-Alpes-Côte d’Azur region, written at the request of Bishop Wadalde between 813 and 814, the aim of the article is to show how, in this context, the opposition between first-borns and second-borns apparently did not play a major role in the organisation of the family and of agricultural work. The source made no distinction whatsoever between elders and youngers brothers and sisters, either in terms of names or in the distribution of work. After a brief presentation of the structure of the document and the population listed in it, we will see how the Church and the families are not interested in establishing a hierarchy based on age between brothers, and how the latter seem to be structured according to practical requirements (the different types of farm they exploit, the tribute to be paid to the Church, etc.) rather than on the basis of possible patterns of primacy of first-borns. On the other hand, we will see how a certain superiority of brothers over sisters was present in rural Provence in the 9th century, independent of the status of second-born or first-born.