Who married Sibylle von Arnim-Krölchendorff?

Count Wilhelm Otto Albrecht von Bismarck-Schönhausen (1 August 1852 – 30 May 1901) was a German counselor, civil servant and politician, who served as a member of the Reichstag from 1880 to 1881 and president of the Regency of Hanover from 1889 to 1890. The youngest son of Otto von Bismarck, he and his brother Herbert von Bismarck both resigned their posts after the elder Bismarck was dismissed as Chancellor of Germany in 1890. Wilhelm subsequently accepted an appointment as Governor of East Prussia in 1894. Mount Wilhelm (German: Wilhelmsberg, or in Kuman: Enduwa Kombuglu, or Kombugl'o Dimbin) the highest mountain in Papua New Guinea at 4,509 metres (14,793 ft), part of the Bismarck Range, was named after him by Hugo Zöller.