“ FERDINAND I., king of Portugal (1345–1383) , sometimes referred to as el Gentil (the Gentleman) , son of Pedro I. of Portugal (who is not to be confounded with his Spanish contemporary Pedro the Cruel) , succeeded his father in 1367. On the death of Pedro of Castile in 1369, Ferdinand, as great-grandson of Sancho IV. by the female line, laid claim to the vacant throne, for which the kings of Aragon and Navarre, and afterwards the duke of Lancaster (married in 1370 to Constance, the eldest daughter of Pedro) , also became competitors. ”