Duke Friedrich August of Oldenburg German duke (1936-2017) (1936–2017) Parents Nikolaus, Hereditary Grand Duke of Oldenburg Princess Helene of Waldeck and Pyrmont Children Rixa, Herzogin von Oldenburg Paul-Wladimir Herzog von Oldenburg Bibiane, Herzogin von Oldenburg Siblings Anton-Günther, Duke of Oldenburg Duchess Eilika of Oldenburg Duchess Altburg of Oldenburg Duke Peter of Oldenburg Duke Johann of Oldenburg Duchess Rixa of Oldenburg Duke Egilmar of Oldenburg Huno Herzog von Oldenburg Partners Donata Countess of Castell-Rüdenhausen Princess Marie Cécile of Prussia