In the high Middle Ages both elite kinship groups and polities became formalized, conceptually as well as legally. Since interdependence continued, there is a connection between the formalization and stabilization of elite families and the growth of more stable and durable polities. As the ruling strata of society became public, visible and relatively transparent, more durable political institutions could be formed. This chapter supports the link between formalized elite families and formalized polities. Kings and queens devoted considerable energies to ruling their realms through the nobility, for example by approving and arranging marriages. The realm depended upon magnate dynasties and their economic, military and political resources. Successful rulers collaborated with nobles. Attempts to forcibly subdue them often resulted in civil war, deposition of the monarch and even more rights for the nobility. This teaches us that collaboration, rather than coercion, is a key to polity formation.