Following the death of Prince Karl Günther of Schwarzburg-Sondershausen on 28 March 1909, the Sondershausen branch became extinct and the Schwarzburg principalities were united in a personal union under Prince Günther Victor of Schwarzburg-Rudolstadt.
După decesul Prințului Karl Günther de Schwarzburg-Sondershausen la 28 martie 1909, ramura Sondershausen s-a stins și principatele Schwarzburg (Schwarzburg-Sondershausen și Schwarzburg-Rudolstadt) s-a unit sub Prințul Günther Victor de Schwarzburg-Rudolstadt.