[1][2] Born in London in 1861, he was the second but eldest surviving son of Mary Harriet (née MacNeile; 1833–1919) and Hugh MacCalmont Cairns, 1st Earl Cairns, a British statesman who served as Lord Chancellor of the United Kingdom during the first two ministries of Benjamin Disraeli.

[2] On 20 November 1884, Cairns was successfully sued for £10,000 for breach of promise of marriage by Emily Mary Finney (an actress with the stage name of May Fortescue).

Fortescue, assisted by W. S. Gilbert's solicitors, sued him for breach of promise, receiving £10,000 in damages.

[7] On 19 December 1887, he was married to Olivia Elizabeth Berens OBE at St. Mary's Church, Bryanston Square, Marylebone, London.

[3] Together, they were the parents of:[8] Cairns died of pneumonia on 14 January 1890, aged 28, at 18 Queen Street, Mayfair, London.