Kingdom of Serbia is Kingdom in Europe (Balkan), they become Kingdom after disspanding of Serbo-Romanian Empire.
Ruler of Serbian Kingdom is member of Saint Nemanjic dinasty. For that dinasty is thikned they are dead, but when Milutin IV eneter in Casle and said he is from Dinasty Nemanjic King's nurse take his DNA to check. After few days resulatats be positive, he is Nemanjic.
Serbia be Kingdom for 30 years. Serbia become Empire when Serbian King Dusan become crowned for Tzar. 30 days after he conque rest of Albania and made Bosnian Christian republic become part of Serbian Empire. He also take Dalmatia from Croatia.