An interesting little quote from 'The House of Ptolemy' by E R Bevan 1927
"One institution of the old Macedonian kingdom, kept up the Ptolemies in Egypt, as in other Hellenistic courts of those days, must have given social prestige to a certain number of families - the practice of bringing up a picked number of boys at court in attendance on sovereign and in close association with the boys of the royal family. They were called paides basilikoi, and in after-life a man who, as a member of this corps, had been the comrade in boyhood of the man now on the throne, might describe himself as the king's syntrophos. An analogous number of girls seem to have been brought up with the little princesses of the royal house.
Possible the title of tropheus ("nurturer") of the king, which we find borne by certain men at the prolemaic court (as at other Hellenistic courts), means that the person in question had had charge of this corps of boys, together with the direction of the little prince, who was now king."