The article focuses on one of the fragments of the relationships between the Armenian Catholicosate and Mleh Prince dating back to the early 70-s of the
XII century. Taking into account the viewpoints existing both in the medieval sources and in the contemporary scientific literature there was made an attemptto thoroughly and deeply introduce the relationships existing between them. The article also makes an attempt to introduce the situation which was created in Hromkla Catholicosate after the death of Nerses Shnorhali. It analysis the struggle for the throne that was between Nerses Shnorhali’s nephews, that was between Grigor Apirat and Grigor IV Tgha. In the process of the analysis there was revealed the role that played Mleh Prince and Nar Ad-din Sultan of Aleppo in the election of the Armenian Catholicos.