Royal Marriage Alliances
Any discussion of the marriage alliances of the Achaemenid royal house must examine the questions whether Achaemenid kings practised polygamy and to what extent they permitted next-of-kin marriages. Polygamy and certain kinds of incestuous marriages were unacceptable in Greek society. The Greeks noticed that the Persian royal family appeared to engage in both and described these practices to emphasize the monstrosity of the Persian king, his decadence, and his domination by women. What seems to have been less well understood by Greek writers were the political motivations that underlay these practices. Both polygamy and endogamic marriages are excellent tools to help concentrate and preserve power; they restrict the families from which a royal wife can be selected, and help to secure male offspring (XPf 28-32; Young 1988b: 71-2; Burn 1984: 277-8).
The various references made to the mother of the king grant her a significant role in relation to the male royal offspring, in particular for the heir to the throne. While references to full brotherhood imply the existence of half-brothers and therefore of other women of the king besides the king's wife, the 'political' parenthood of a successor to the throne points to the fact that his mother carried a political weight which exceeded that of other women. If we assume that there were other 'royal women' we must inquire how they were distinguished from the king's wife, whether they were married to the king, which would indicate the existence of polygamy, or whether they were not married and only held the status of 'concubines of the king'.
Near Eastern evidence for the Persian period unfortunately does little to assist us in answering these questions. The best-known Greek evidence comes from Herodotus according to whom each