After their father's death in 1365, Nicholas III and his three brothers initially ruled their inheritance jointly.
In 1367, however, the inheritance was divided: the oldest brother, John I, received the Duchy of Racibórz, while the three younger brothers, Nicholas III, Wenceslaus I and Przemko I continued to jointly rule the Duchy of Opava.
In 1377, Opava was split, with Nicholas III and Wenceslaus I jointly ruling the newly split off Duchy of Głubczyce and Přemek I ruling what remained of the Duchy of Opava.
As Nicholas III was continually in financial difficulties, he had to mortgage the districts of Głubczyce, Zlate Hory, Hlučín and Krzanowice to his uncle Conrad II of Oels.
His youngest brother Přemysl I continued to rule the Duchy of Głubczyce.