Born Geoffrey George Gordon FitzClarence, he was the son of William FitzClarence, 2nd Earl of Munster (19 May 1824 – 30 April 1901) and Wilhelmina Kennedy-Erskine (27 June 1830 – 9 October 1906). His parents were first cousins, thus making Geoffrey a great-grandson of William IV twice over.
Geoffrey was the third son of nine children. Edward died at the age of 14, Lionel as a young child. Lord Tewkesbury was commissioned into the British Army as a subaltern of the 2nd Battalion King"s Royal Rifle Corps (then the 60th Rifles).
He served in the Second Anglo-Afghan War in 1879-1880 at the age of 19, was present at the engagement at Ahmed Kheyl, and Uraco, near Ghaznee, and accompanied Lord Roberts in the march to Kandahar, and was present at the battle of that name.
He also saw some service with the third battalion of his regiment in the First Boer War in 1881. He became captain in 1888 and resigned his commission in the Regular Forces in 1895.
After his retirement he joined the Militia Battalion of the Royal Scots, and after some years´service in command of a company was promoted to the rank of major. lieutenant was during this last engagement that he received notice of his father"s death and his succession to the Munster title.
He never returned to the United Kingdom to take his place, dying in South Africa just nine months after succeeding his father, at the age of 42, from an accident at Lace Mines.
