The formation within the framework of the Arab vilayet of Armīniya, which consisted of historical Greater-Armenian, Caucasian Albanian and Iberian lands, Bagratid numerous autonomous principalities, is defined in this article, for the first time in the scientific historiography, as genesis “pan-Bagratid family federation”. Author represents an attempt at establishing the actual time of migration of the some representatives of the Armenian naxarar house of Bagratuni to Arab Ǧurzān and Arab Arrān as well as the geography of their new domains in those regions. Finally, he determines the exact time of legal formalization of the so-called “pan-Bagratid family federation” by the caliph administration.