First marriage

On 1 May 1902,^[1] she married her first husband, Alfredo Huberto Duggan (1875–1915), a first generation Irish Argentine from Buenos Aires. In 1905, Duggan was appointed to the Argentine Legation in London where the family thereafter moved. Together, they were the parents of three children, two sons and a daughter:^[7]

• Alfred Duggan (1903–1964),^[8] a historical novelist who was the best-selling historical novelist during the 1950s.^[8]
• Hubert Duggan (1904–1943),^[9] who later became a British Member of Parliament and married Joan Dunn, the daughter of Sir James Dunn.^[9]
• Grace Lucille Marcella Duggan (1907–1995), who married Edward Denis Rice,^[10] and was the mother of Caroline Helen Rice (1931-2016), wife of Robert Windsor-Clive, 3rd Earl of Plymouth.^[11]

When Grace was presented at Court, she stood behind fellow American Nancy Langhorne Shaw, who later became Viscountess Astor upon her marriage to Waldorf Astor, 2nd Viscount Astor in 1906 (and later an MP in her own right).^[6] She was also a friend of Lady Randolph Churchill, the American-born mother of Winston Churchill, and Consuelo Vanderbilt, the wife of the 9th Duke of Marlborough.^[6]

Grace Duggan was a wealthy woman after her husband's death in 1915, inheriting an estate of more than $18,000,000,^[9] which included eighteen large estancias in South America. In 1916, Philip Alexius de László painted her as a widow.^[12]

Second marriage

On 2 Jan 1917, aged 37, she became the second wife of Lord Curzon. On the occasion of their marriage, Lord Curzon bought Bodiam Castle in East Sussex, a 14th-century building that had been gutted during the English Civil War. They restored it extensively, then bequeathed it to the National Trust.^[13] In 1923, when Curzon was passed over for the office of Prime Minister partly on the advice of Arthur Balfour, Balfour joked that Curzon 'has lost the hope of glory but he still possesses the means of Grace".^[14]

Curzon had three daughters from his first marriage to Mary Victoria Leiter, Baroness Curzon of Kedleston: Mary Irene, Lady Ravensdale (born 20 January 1896); Cynthia Blanche (born 23 August 1898), the first wife of Sir Oswald Mosley; and Alexandra Naldera (born 20 April 1904), the wife of Edward Dudley Metcalfe, the best friend, best man and equerry of King Edward VIII.^[15][16]

Despite her fertility-related operations and several miscarriages, the couple did not produce an heir. This eroded their marriage, which ended in separation but not divorce.^[17] Letters from Curzon to Grace in the early 1920s indicate that they remained devoted to each other.^[18] However, Oswald Mosley admitted privately that he had an affair with Lady Curzon, as well as with her step-daughters, Alexandra and Irene.^[19]