 He was the third son of William Trench, 3rd Earl of Clancarty and Lady Sarah Juliana Butler.He married Harriet Maria Georgina Martins, daughter of Sir William Martins, on 21 April 1864.He fought in the Second Opium War between 1857 and 1858, commanding a ladder company at the capture of Guangzhou and Nankow, and was mentioned in despatches.