By about 1180/82 he assumed the title of Duke of Merania, referring to the Adriatic seacoast of Kvarner which his ancestors had conquered in the 1060s and annexed to Istria and Carniola.

[2] His father had been a loyal vassal of Emperor Frederick Barbarossa and in turn was enfeoffed with the Istrian march upon the death of the Sponheim margrave Engelbert III.

[3] The rule over the self-styled "Merania" actually encompassed the same area as the old Istrian margraviate, and did not constitute a separate administrative or political entity; however, its ruler gained prestige from his new ducal title, and the comital House of Andechs was elevated to Princes of the Holy Roman Empire.

About 1180, Berthold married Agnes of Rochlitz,[2] a daughter of Margrave Dedi III of Lusatia from the Saxon House of Wettin.

There it was negotiated that a daughter of Berthold would marry Tohu, son of Prince Miroslav of Zahumlje on the feast of Saint George next (24 April 1190).