Peter IV was King of Aragon from 1336 until his death and also King of Sardinia and Corsica (as Peter I), King of Valencia (as Peter II), and Count of Barcelona (and the rest of the Principality of Catalonia as Peter III). In 1344, he deposed James III of Majorca and made himself King of Majorca.
Peter was born at Balaguer, the eldest son, and heir of Alfons IV, then Count of Urgell, and his first wife, Teresa dentenca. Peter was designated to inherit all of his father's title save that of Urgell, which went to his younger brother James.
His reign was occupied with attempts to strengthen the crown against the Union of Aragon and other such devices of the nobility, with their near-constant revolts, and with foreign wars, in Sardinia, Sicily, the Mezzogiorno, Greece, and the Balearics. His wars in Greece made him Duke of Athens and Neopatria in 1381.
Depicted above is a Sardinian ducat of Peter IV's reign. It illustrates the four bars representing the Crown of Aragon.
Image Source: Wikipedia.org