Christian August II, Duke of Schleswig-Holstein-Sonderburg-Augustenburg (19 July 1798 – 11 March 1869, Christian Carl Frederik August), commonly known as Christian, Duke of Augustenborg, was a Danish/German prince and statesman. During the 1850s and 1860s, he was a claimant to first duke of the whole provinces of Schleswig and Holstein, and a candidate to become king of Denmark following the death of King Frederick VII. He was the father-in-law of Princess Helena (daughter of Queen Victoria) and the paternal grandfather of Augusta Victoria, German Empress and wife of Kaiser Wilhelm II. Source: Wikipedia (en)