Educated at Harrow, for a while he was an officer in the Rifle Brigade and volunteer A.D.C. to the king 1901-1902. On 29 May 1871 at St.Michael's, Worcester, he married by banns an actress, Kate Walsh, who was known as Kate Cooke. In 1878 they separated, starting divorce proceedings in 1884. At this time it was found that Kate Cooke had previously gone through the form of marriage, 6 July 1863, with George Manby Smith, a commercial traveller, who was still alive in 1871 when 
Kate Cooke married the Earl of Euston. However, as George Manby Smith had married Mary Anne Johnson on 26 June 1862, the marriage between Kate Cooke and George Manby Smith was invalid and so her marriage to Lord Euston was still valid. 
The Earl of Euston was a prominent Freemason, being Grand Master of the Mark Masons. In 1912 he died of dropsy and, as he had no children, a younger brother became heir to their father and eventually 7th Duke of Grafton. 
 

Source: Leo van de Pas