He is married to Hedwig Anna Karoline Wilhemine Clementine von SIERSTORPFF-CRAMM.
They got married on May 12, 1896 at Driburg, j. 33014 Bad Driburg, he was 35 years old.
http://trees.ancestry.com/pt/AMTCitationRedir.aspx?tid=114784053&pid=794
Graf [Count] Wilhelm Karl Ludwig Kuno von Oeynhausen-Sierstorpff<br>Gender: Male<br>Birth: July 18 1860 - Dömitz, Ludwigslust, Mecklenburg-Vorpommern, Germany<br>Death: Apr 1 1922 - Hamm, Hamm, Nordrhein-Westfalen, Germany<br>Wife: Hedwig Freiin von Oeynhausen-Sierstorpff (born von Sierstorpff-Cramm)<br>Children: Gräfin [Countess] Walburg Anna Therese Regelind Antonie Ludmilla Van Praagh (born von Oeynhausen), Gräfin [Countess] Gerda-Ursula Antonie Klementine Edith Hedwig-Luise Julie Susanne Wanda von Oeynhausen-Sierstorpff, Graf [Count] Rabe-Caspar-Heinrich Oeynhausen-Sierstorpff, Gräfin [Countess]von Aspern (born von Oeynhausen) , Gräfin [Countess] Susanne Marie Richarda Luise Annette Edgarda Friederike Irma Erika von Oeynhausen-Sierstorpff, Gräfin [Countess] Leonor Benedikta von Prollius (born Oeynhausen)