A Dictionary of Greek and Roman biography and mythology

3. A son of the preceding, who held the office of body-guard (Somatophylax) to the young king, Ptolemy Epiphanes; a post which Agathocles suffered him to retain (probably on account of his youth) even after the death of his father. In the tumult which led to the destruction of Agathocles, Sosibius took a decisive part, by appealing to the infant monarch himself to give up his hated favourites to the populace; and it was probably on this account that he subsequently obtained the guardianship of the young king's person, with the custody of the royal signet. These duties he discharged in a manner that gave general satisfaction ; but the intrigues of his more turbulent and ambitious brother, Ptolemy, having involved him in an open rupture with Tlepolemus, who was at the head of the administration, the latter obtained the advantage, and compelled Sosibius to resign his office; from which time we hear no more of him. (Plb. 15.32. 16.22.)

[E.H.B]