Kavis/Kayanids are amongst the most important building-blocks of the ancient Iranian culture. The Avestan texts reveal the royal character of Kavis. However, myths of Kauui-Usan/KayUs reveal a Proto-Indo-Iranian inheritance. It is argued that the Avestan texts hint to distinguishing legends of Kauui-Usan/KayUs not to be an integral part of the proper Kayanid dynasty. Also, it is argued that the house of Kauui Vištāspa of the Old Avestan period antedate considerably the proper Kayanid dynasty, which is to be placed in the Young Avestan period. The enumerated traits of the Kayanid dynasty in particular Kauui Haosrauuah in Avestan texts lead to an appreciation of their role in the genesis of Iranian nationality. The historiography evident in the Avestan texts and the place of the Kayanid dynasty in it make it probable that this ideological historiography originated from the Kayanids. In other words, unification of Iranian countries under Kauui Haosrauuah and victory over Turiias were seen as the ultimate encounter of dualism of good and evil mirroring the slaying of Aži Dahāka by Θraētaona. In post-Avestan period, KayUs who was probably the eponym of the Kayanids was diffused into the dynasty. Likewise, the house of kauui Vištāspa was thought of a minor branch of Kayanid dynasty, post-dating the main dynasty and similarly as national Iranian kings. As such, representation of Kavis as a continuous dynasty evident in the Middle Persian and the Perso-Arabic literature is an outcome of evolution of the oral tradition amongst Iranians.