Joachim Franz Humbert was born in Potsdam on 17 December 1890 and was the sixth son of Wilhelm II, German Emperor, and Augusta Victoria of Schleswig-Holstein.
The empress went into premature labour with Joachim after an argument with her sister-in-law, Sophie of Prussia, who was married to the future Constantine I of Greece. Sophie had not converted to the Orthodox faith at the beginning of her marriage but after the birth of her eldest son, she decided it was time to embrace the faith of her subjects. After receiving the blessing of her mother, Victoria, Princess Royal, and her grandmother, Queen Victoria, Sophie broke the news to her brother, Wilhelm, at a family wedding but he reacted badly. Augusta Victoria tried to persuade Sophie to change her mind but a heated argument between broke out between the two women and the empress went into labour.
As a result of the premature birth, Wilhelm and Augusta Victoria remained overprotective of Joachim for the rest of his life and they never forgave Sophie. Joachim grew up alongside his older brothers but he was soon followed by a younger sister, Viktoria Louise, who was the only girl in the family. During the First World War, Joachim served as a cavalry officer but he was wounded at the First Battle of the Marne in 1914 and he then served with intelligence.
Joachim married Marie Auguste, the eldest surviving daughter of Eduard, Duke of Anhalt, and Louise Charlotte of Saxe-Altenburg, in Berlin on 11 March 1916. The couple had one son, Karl Franz, who was born on 15 December 1916, but the couple announced their intention to divorce just after the end of the war. Unable to accept the abolition of the monarchy and the loss in his status, Joachim soon fell into a depression and shot himself on 18 July 1920. Joachim’s suicide deeply affected his mother to the point her health began to fail and she died on 11 April 1921.
After Joachim’s death, Karl Franz was taken into the custody of his uncle, Eitel Friedrich, who was now head of the House of Hohenzollern, however the boy was returned to his mother in 1921 after a court declared the act had been unlawful. There were reports Marie Auguste had run away from both her husband and her child during the war and had been forcibly brought back by the kaiser before later filing for divorce but these rumours are unsubstantiated. The following year, Marie Auguste sued her former father-in-law for the financial support she should have received as part of her marriage contract but the kaiser’s lawyers argued the House of Hohenzollern no longer had an obligation due to reduced circumstances.