Apparently George preferred his mistress (above his 2nd wife among others):https://en.wikipedia.org/..._6th_Duke_of_Leuchtenberg
"..When still married to his second wife, George moved in with his French mistress, to the great anger of the morally upright Emperor Alexander III. When told that George was spending his vacations at the coastal town of Biarritz in south-western France, Alexander declared "So the prince is washing his filthy body in the waves of the ocean".
Their marriage was considered "tempestuous and stormy," with George reportedly "insult[ing] and outrag[ing] her from the very first day of their marriage". Anastasia was able to obtain a divorce from him several years into their marriage, on 15 November 1906. Various sources attribute George to have been good-looking but a "stupid and rather sorry individual", although these reports were most often in connection with his second wife, who, when arranging her divorce from George, was widely reported to want to do so because she could no longer live with a man of "intolerable stupidity". Anastasia later remarried to Grand Duke Nicholas Nikolaevich of Russia, a grandson of Nicholas I of Russia (and on his mother's side a nephew of George's first wife Theresa). She and her sister became famous in Russian society as the "black peril" so called because of their home country of Montenegro, their dark complexions and their interest in occult...."
"..In 1901, through either the deaths or morganatic marriages of his elder brothers, George became the head of the Russian branch of the House of Beauharnais. At the turn of the twentieth century, when still married to Princess Anastasia of Montenegro, George was considered as a possible successor to the childless Alexander I of Serbia. Alexander was overthrown and murdered in a military coup, and succeeded by Peter I of Serbia..."