Abstract: (Kinship relations in Romance languages: a diachronical and compared approach) This paper aims to study from a diachronic and compared point of view the evolution of the lexical field of blood kinship relations starting from Latin to five most important romance languages: Spanish, Portuguese, French, Italian and Romanian. Although this topic has been analyzed synchronically in some Romance languages, there has not been yet a diachronic and compared vision. We would like to pursue not only an onomosiological approach (What happened with the significants pater, mater, filius, avus, etc., if they survived? Is there a lexical continuity?), but also a semasiological one (What forms occupy today the places of the initial structure? Are there any empty spots? Did the field incorporated other terms that initially were not integrated in this structure? What are the most important lexical changes?). It is also interesting to compare the different structures in the Romance languages from the point of view of the meaning.