As was the case with almost all royal families, marriage politics in the "Casa Condal de Barcelona y Real de Aragón" were constantly subject to change: in connection with particular interests at a given moment, the socio-political climate at the time or for purely personal reasons. An attempt has been made to cover the marriages forged by the Kings of Aragon and Counts of Barcelona, from the death of Peter the Catholic in 1213 up until the time of Ferdinand the Catholic, as well as by other members of the royal familiar who were used to secure friendships, consolidate alliances and to clear the way for or shape future conflicts. Reasons of state remained supreme although passion sometimes interfered. An attempt has been made to analyse each specific case and the impact on government throughout the different kingdoms which constituted the Crown of Aragon.