Passage 1.7.1
οὗτος ὁ Πτολεμαῖος Ἀρσινόης ἀδελφῆς ἀμφοτέρωθεν ἐρασθεὶς ἔγημεν αὐτήν, Μακεδόσιν οὐδαμῶς ποιῶν νομιζόμενα, Αἰγυπτίοις μέντοι ὧν ἦρχε. δεύτερα δὲ ἀδελφὸν ἀπέκτεινεν Ἀργαῖον ἐπιβουλεύοντα, ὡς λέγεται, καὶ τὸν Ἀλεξάνδρου νεκρὸν οὗτος ὁ καταγαγὼν ἦν ἐκ Μέμφιδος· ἀπέκτεινε δὲ καὶ ἄλλον ἀδελφὸν γεγονότα ἐξ Εὐρυδίκης, Κυπρίους ἀφιστάντα αἰσθόμενος. Μάγας δὲ ἀδελφὸς ὁμομήτριος Πτολεμαίου παρὰ Βερενίκης τῆς μητρὸς ἀξιωθεὶς ἐπιτροπεύειν Κυρήνην--- ἐγεγόνει δὲ ἐκ Φιλίππου τῇ Βερενίκῃ Μακεδόνος μέν, ἄλλως δὲ ἀγνώστου καὶ ἑνὸς τοῦ δήμου---, τότε δὴ οὗτος ὁ Μάγας ἀποστήσας Πτολεμαίου Κυρηναίους ἤλαυνεν ἐπʼ Αἴγυπτον.
This Ptolemy fell in love reciprocally with his sister Arsinoe and married her, doing thus things entirely alien to Macedonian practice, but consistent with Egyptian traditions, of the people over whom he ruled. Furthermore, he put to death a second brother, Argaeus, who, it is said, had plotted against him, and it was this Ptolemy who transferred the corpse of Alexander from Memphis. He likewise killed another brother, the son of Eurydice, when he discovered that he was planning a revolt among the Cyprians. However, Magas, his maternal half-brother by his mother, Berenice—who had been designated governor of Cyrene (Magas was born to Berenice by Philip, a Macedonian otherwise obscure, from among the common people)—this Magas rebelled against Ptolemy, having won over the Cyreneans, and marched against Egypt.