John Röhl's authoritative biography of Kaiser Wilhelm II includes an account of Ernst Gunther and his relationship with his sister, Augusta Viktoria, and brother-in-law, Wilhelm II.
The relationship proved to be "problematic," after the Duke's secondment to the General staff in "the summer of 1890 had already attracted criticism. A year later, there was further outrage when the Kaiser promoted his brother-in-law to captain on the General Staff.
"The person in question is utterly lacking in both training and competence," was the comment about Ernst Gunther's promotion. Others on the General staff thought that the Kaiser should promote his brother-in-law as a "fully fledged General staff officer" was a seen as a "slap in the face."
Ernst Gunther, in spite of this promotion, "always felt slighted" by Wilhelm and by other members of the German royal family "and by other royals of his own rank."
He was not invited to the wedding of his cousin, Princess Marie Louise, to Prince Aribert of Anhalt.
He was considered "unusually immature and conceited." Empress Friedrich thought him a "most foolish young man." The Kaiser's younger sister, Moretta, described him as "an idiot."
The young duke accompanied the Kaiser and Kaiserin on a visit to England in July 1891, where he seen to be arrogant, rude, and his behavior was outrageous.
When Dona married the the future Kaiser, Ernst Gunther received a "donation of a million marks, along with his annual appanage of 300,000. He also had a "private income of about 200,000." Yet Ernst Gunther was always in debt, partially due to "ill-advised building projects." Even after he reached the rank of major, he was "still up to his ears in debt."
Apparently the "greatest embarrassment for Dona and Wilhelm was Ernst Gunther's "obsessive and tempestuous" search for a wife. In 1890, he visited his Uncle Christian and Aunt Helena, with the hope of finding an English bride. He knew he would not be acceptable for the daughters of the Prince and Princess of Wales, but he was eager to marry "one of the daughters of the country, provided she were well brought up..."
Princess May of Teck, the daughter of Queen Victoria's first cousin, Princess Mary Adelaide of Cambridge, was suggested as a possible bride, but when Dona found out, she was horrified. She would not allow her brother to make "such a mésalliance."
In 1893, Ernst Gunther "horrified" his brother-in-law and sister by proposing to Laetitia, Duchess of Aosta, a widow. The proposal took place in Paris, but thanks to the intervention of the Count Münster, the German Ambassador, the engagement with the Bonaparte princess was quickly ended. A year later, the duke "tried his luck" with Princess Helene of Orléans.
Dona was tears at the thought of this marriage. The Kaiser, under any circumstances, would approve a marriage with a member of the House of Orléans, and considered the arrangement to be an intrigue by the Orléans family who wanted "make themselves a good name through the House of Hohenzollern."
Prince Philipp zu Eulenberg despaired, and described Ernst Gunther was "like a rutting stag in spring. Perhaps even stupider."
Bernhard von Bülow saw Helene as a "perfidious princess," and dangerous. Ernst Gunther would be "wax in her hands." The Orléans family were zealous Roman Catholics and they would "create a focus of anti-national ultramontane elements in Berlin."
The Kaiser made it clear that he never give his consent to the marriage, and he would never receive Ernst Gunther and his wife, or allow them to live in Prussia, "in particular Schleswig-Holsein."
In the end, the fear was for naught. On June 25, 1895, Princess Helene married the Duke of Aosta.
Ernst Gunther turns his attention to 18-year old Johanna von Spitzemberg, who was not of royal birth. The Duke was determined to marry the young noblewoman. Philipp zu Eulenberg sent a telegraph to the Kaiser in Palermo. No surprise here: the Kaiser was furious. Johanna was the niece of Baron Axel von Varnbüler, Württemberg's envoy.
The Kaiser telegraphed in response: "Please warn Axel at once. His niece is too good for such a wretch." Eventually, the Kaiser called upon Johanna's uncle to help end the affair. At the same time, Wilhelm II continued to arrange a marriage between his brother-in-law and Countess Anna Görtz, but this arrangement came to nought as well.
It was in August 1898, when Ernst Gunther married sixteen-year-old Princess Dorothea of Saxe-Coburg and Gotha. This marriage was also seen to be "problematic." Prince Henry of Prussia, the Kaiser's younger brother, wrote from Russia that he was glad that his mother had not attended the wedding of that "d--d fool to a child."
The outrage was made greater because the engagement coincided with Princess Dora's mother, Princess Louise, being sent to an asylum, and Louise's lover arrested for fraud.
In spite of all his attempts to marry, Ernst Gunther's life edged from scandal to scandal. He had connections with "ladies of the demi-monde. The marriage with Dorothea of Saxe-Coburg and Gotha was not a success. Dora was too young to understand how to a wife to such an unsuitable man. She was an eventual heiress to the entailed estate of her father, Prince Philipp, who had inherited great wealth from his parents, Prince August and Princess Clementine of Orleans.