On 22 August 1893, following the death of Ernest II, Duke of Saxe-Coburg and Gotha, Beatrice's father's uncle, the vacant duchy fell to her father, as Albert Edward, then Prince of Wales and future King Edward VII of the United Kingdom, had renounced his rights to the duchy in favor of succession to the British crown.

She was a bridesmaid at the wedding of their paternal cousins the Duke and Duchess of York (the future King George V and Queen Mary) on 6 July 1893.

[3]In 1902, Princess Beatrice had a romance with Russian Grand Duke Michael, the younger brother of Tsar Nicholas II, and at that time the heir presumptive to the Imperial Throne.

She began receiving letters from him in September 1902 and, although he was a Russian Grand Duke and she now a German Princess, they corresponded in English, and he nicknamed her "Sima".

Although such marriages had been allowed previously in the House of Romanov (Grand Duchess Catherine Pavlovna, whose hand was denied to Napoleon I, was twice allowed to wed first cousins; her descendants became the Russian branch of the Dukes of Oldenburg), the devout Nicholas II, official head of Russia's church, refused to relax the rules for the sake of his brother.

The situation was aggravated by a letter Beatrice then received from her elder sister Victoria Melita ("Ducky"), in which Michael was blamed for having callously initiated the doomed romance (when, a couple of years later Ducky, having divorced her first cousin Ernest Louis, Grand Duke of Hesse, was told that remarriage to another first cousin, Grand Duke Kirill Vladimirovich, would likewise be forbidden by the Tsar, she refused to take no for an answer; the couple eloped into exile).

The Spanish government objected to an infante's proposed match with a British Princess who, unlike Queen Victoria Eugenie, had not agreed to convert to Roman Catholicism: the King was obliged to make clear that, should the wedding take place, the couple would have to live in exile.

[citation needed] Nonetheless, Beatrice and Alfonso married in a Roman Catholic and Lutheran ceremony at Coburg on 15 July 1909.

Beatrice and Alfonso lost their estate during the war and the couple's middle son, Alonso, was killed fighting for the fascist forces.