He was born 13 November 1871 at Simla in India. Until 1883 he was Earl of Sunderland, and the Marquess of Blandford from 1883 until 1892. His nickname of "Sunny" came from his title of Earl of Sunderland. In later life he complained that he had been bullied by his father, but according to an aunt he had been a most charming boy who had lost his spirits.
In December 1893 his mother unsuccessfully petitioned the Court for his upkeep as the Duke, his father, failed to do so. However he was still educated at Winchester and Cambridge. His father died in 1892 and he became the 9th Duke of Marlborough.
While both were in love with someone else, he married the 18-year-old Consuelo Vanderbilt. "There was no need for sentiment", was his opinion. After the marriage he received $1.6 million in cash
and the income from $2 million invested in stock. Later, other gifts brought the total Vanderbilt contributions to $20 million. Within two years two sons were born.
Consuelo felt out of place and unaccepted by Britain's aristocracy. Dinner with her husband was always spent in silence as she found him cold and callous, although for others he was popular and amiable. In 1897 Marlborough met Gladys Deacon for the first time. Being quite taken with her, he invited her to stay at Blenheim where Gladys and Consuelo were introduced, resulting in a friendship that lasted for many years. About 1901 the Prussian Crown Prince came to England and
fell in love with Gladys. In September 1902 Consuelo and Gladys toured through Germany where they were escorted by an Imperial A.D.C. whose main task was to assure that no meetings took place between Gladys and the Crown Prince. Apparently Gladys liked Germans while Consuelo
detested them.
In August 1906 Gladys declared that she was engaged to Lord Brooke but this came to nothing. At the same time the marriage of the Duke and Duchess of Marlborough failed and in January 1907 they were legally separated, to be divorced in 1921. Consuelo then married Jacques Balsan while Gladys Deacon married the Duke.
Marlborough was a good Landlord at Blenheim and made many improvements both to the estate and the house. As a conservative he held minor parliamentary posts and, during the South African war, was assistant military secretary to Lord Roberts. However he left after a while to go to South Africa where, with his cousin Winston, he marched on Pretoria. He returned to military service during the first World War and served in France. In 1934 he died of cancer.
 

Source: Leo van de Pas