Alexander Karađorđević was born on 16 December 1888 in the Principality of Montenegro as the fourth child (second son) of Peter Karađorđević (son of Prince)
Alexander of Serbia who thirty years earlier in 1858 was forced to abdicate and surrender power in Serbia to the rival House of Obrenović) and Princess Zorka of Montenegro (eldest daughter of Prince Nicholas of Montenegro). Despite enjoying support from the Russian Empire, at the time of Alexander’s birth and early childhood, the House of Karađorđević was in political exile, with family members scattered all over Europe, unable to return to Serbia.
Serbia had recently been transformed from a principality into a kingdom under the Obrenovićs, who ruled with strong support from Austria-Hungary. The antagonism between the two rival royal houses was such that after the assassination of Prince Mihailo Obrenović in 1868 (an event Karađorđevićs were suspected of taking part in), the Obrenovićs resorted to making constitutional changes, specifically proclaiming the Karađorđevićs banned from entering Serbia and stripping them of their civic rights.
Alexander was two when his mother Princess Zorka died in 1890 from complications while giving birth to his younger brother Andrija, who died 23 days later.
Alex ander spent his childhood in Montenegro. In 1894 his widower father took the four children, including Alexnder, to Geneva where the young man completed his elementary education. Alongside his older brother George, he continued his schooling at the imperial Page Corps in St Petersburg, Russian Empire. The British historian Robert Seton-Watson described Alexander as becoming a Russophile during his time in St. Petersburg, feeling much gratitude for the willingness of the Emperor Nicholas II to give him a refuge, where he was treated with much honor and respect.
As a page, Alexader was described as hard-working and determined while also being a “loner” who kept to himself and rarely showed his feelings.Being a Karađorđević led to Alexander being invited by Nicholas II to dinner at the Winter Palace, where he was the guest of honor at meals hosted by the Russian imperial family, which was a great honor for a prince from Serbia’s deposed royal family.
During his time in St. Petersburg, Alexander visited the Alexander Nevsky Monastery, where the abbot gave Alexander an icon of Prince Alexander Nevsky and guided him to the grave of Marshal Alexander Suvorov.After his visit to the monastery, Alexander expressed the wish to be a great general like Marshal Suvorov or Prince Alexander Nevsky, saying he wanted to be commanding either a great army or a great armada when he was a man.
In 1903, while young George and Alexander were in school, their father and a slew of conspirators pulled off a bloody coup d’état in the Kingdom of Serbia known as the May Overthrow in which King Alexander and Queen Draga were murdered and dismembered. The House of Karađorđević thus retook the Serbian throne after forty-five years and Alexander’s 58-year-old father became king of Serbia, prompting George’s and Alexander’s return to Serbia to continue their studies. After Alexander’s 15th birthday, King Peter had Alexander enlisted into the Royal Serbian Army as a private with instructions to his officers to only promote his son if he proved worthy. On 25 March 1909, Alexander was suddenly recalled to Belgrade by his father with no explanation offered other than that he had an important announcement for his son