The couple had five sons before divorcing in October 1917: Their eldest surviving son Prince Michael of Montenegro, succeeded Mirko in the Montenegrin royal succession and would become head of the House of Petrović-Njegoš and pretender to the Montenegrin throne.

[3] Following the assassination of Alexander and Draga in 1903, the resulting conferral of the crown was given to Peter Karađorđević, his brother-in-law.

In 1911 he joined the Black Hand "Unity or Death" secret society which sought the unification of all Serbs in the Balkans, especially those under Austria-Hungary.

Following his death, his ten-year-old son Prince Michael of Montenegro was raised in Paris by his mother and the residual members of the exiled Montenegrin Royal Family.

In 1921 following the death of Mirko's father and shortly afterwards by the renouncement of the defunct throne by former Crown Prince Danilo, the thirteen-year-old Prince Michael of Montenegro became the head of the Petrović-Njegoš house, albeit initially under a pretense regency.