The twice-married aristocrat, formerly known as the Marquess of Blandford, married his second wife, Welsh ceramicist Edla Griffiths, in 2002.
They are said to have met while she was living in Chelsea and working on her art, and they wed after dating for seven years.
The pair are thought to have separated in 2024.
He inherited his dukedom in 2014, following the death of his father, the 11th Duke of Marlborough.
He is a first cousin, three times removed, of Sir Winston Churchill and a distant relative of the late Princess Diana through the Spencer family.
