The full family name is Haugwitz-Hardenberg-Reventlow.
His great great great grandmother, in her times Scandinavia's richest heiress Juliane Frederikke Christiane née Countess Reventlow was divorced from her husband, Prince Karl August Hardenberg, who among other things was Hanoverian envoy in London, because of an affair with the Prince Regent (George IV).
His grand father Count Curt Ulrich Heinrich von Haugwitz, was the last non-royal to be made a Danish count. Because of his marriage to Princess Lucie Caroline of Schönaich-Carolath, heiress of the County of Hardenberg, Christian IX made him Count Haugwitz-Hardenberg-Reventlow in 1885.
The County of Hardenberg compromized the manors of Krenkerup, Christiansdal, Nielstrup, Rosenlund, Nørregård and Sæbyholm on the island of Lolland. Was these one of the Danish estates Barbara and Curt briefly resided on, according to one source? Since Curt's father was a younger son, they were controlled by Curt's uncle and cousin.