The article is devoted to descent of power in the east Slavs state forming at that time. Using material of different sources, first of all, folklore, the author gives a seeing of the plot "Father fights a son", proving that we see a reflection of ceremonial duel of old and young leaders for the power. For all that, historico-genetic, historico-comparative and structural-functional methods of research are used. Ilya Murometz, which must be characterized as an actual ruler of the early state, and his son (daughter), belong to two exogamy's commons, being in relations of enmity and marriage exchange. These potestical-political realities determined that east Slavs of the examined epoch had some features of maternal family period.