Prince Hermann is the elder son of the late Prince Karl of Leiningen and Princess Marie Louise of Bulgaria. He is a descendant of Queen Victoria through his father, who was the son of Grand Duchess Marie of Russia and the Prince of Leiningen. Grand Duchess Marie was the eldest child of Princess Victoria Melita of Edinburgh and Grand Duke Kirill of Russia. Princess Victoria Melita was the third child of Prince Alfred, Duke of Edinburgh, Duke of Saxe-Coburg and Gotha, and Grand Duchess Marie Alexandrovna of Russia.
The Duke of Edinburgh was the fourth child of Queen Victoria and Prince Albert of Saxe-Coburg and Gotha.