Nepos, Lives of Excellent Commanders Preface 3-4
Those who complain about Nepos including supposedly trivial details of Greek commanders’ lives actually reveal their own lack of understanding about Greek customs!
hi si didicerint non eadem omnibus esse honesta atque turpia, sed omnia maiorum institutis iudicari, non admirabuntur nos in Graiorum virtutibus exponendis mores eorum secutos. neque enim Cimoni fuit turpe, Atheniensium summo viro, sororem germanam habere in matrimonio, quippe cum cives eius eodem uterentur instituto. at id quidem nostris moribus nefas habetur.
If these people will learn that the same things are not honourable or dishonourable among all people, but that all things are judged according to one’s forefathers’ ordinances, they will not wonder that we, in setting out the virtues of Greek men, have followed the Greeks’ customs. For it was not a disgrace for Cimon (an eminent man among the Athenians) to marry his half-sister by the same father, since his fellow-citizens followed the same practice. But that would be considered an impious sin according to our customs.