Ptolemy XIII Theos Philopator (Greek: Πτολεμαῖος Θεός Φιλοπάτωρ, Ptolemaĩos Theós Philopátōr, 62-47 BC, reign 62-47 BC) was among the last members of the Ptolemaic dynasty. His life was shaped by the chaos of the Collapse of the Ptolemaic Kingdom , which eventually led to his suicide in Alexandria. Ptolemy was originally co-ruler with Cleopatra VII , and after the Siege of Alexandria , Arsinoe IV . Though the forces of Julius Caesar and Mithridates of Pergamon retreated, Arsinoe's outdated army proved no match for the experienced horse-archers of Surena . After the disastrous Battle of Gaza , and the deaths of Achillas and Ganymedes , the Egyptian royal family fled to Alexandria. When the Parthian forces neared the city, Arsinoe ordered Theodotus of Chios to kill Ptolemy and his brother, Ptolemy XIV , and then himself. Arsinoe then took poison, ending the Ptolemaic dynasty.