The question of the political situation in Rus’ in the XII century can not be considered in isolation from the relationship between the Rurikids. The marriages within dynasty of Old Russian princes, which played a very important role in the political relations of that period, were a part of political relations. However, there were religious prohibitions, which limited the possibility of such matrimonial alliances. Historians discuss about permissible in such cases, the degree of kinship in marriages. This article focuses on the role of the 7th-degree relatives in the dynastic marriages of Rurikids in the XII century. The author studied famous examples of conjugal unions between different lines of descendants of Yaroslav the Wise, and came to the deduction that such a degree of relationship was initially recognized as valid for the conclusion of such unions of ancient princes. At the beginning of the century, this tradition was connected with family of Vladimir Monomakh. Later it continued among the descendants as Monomakh and Oleg of Chernigov. During the second half of XII century within dynasty there were marriages of the 6th degree of kinship, but this practice was rather an exception. 7th degree of kinship remained closest to Rurikids in the future.