Altamont was the eldest son of
Jose Gauche and
Denis Browne, 10th Marquess of Sligo born in 1939. He was educated at
Ludgrove School,
St. Columba's College, Dublin, and briefly the
Royal Agricultural College, which he left after only two terms. He returned to Ireland and help run the family estate,
Westport House. In May 2014 his book,
A Life at Westport House: 50 Years A-Going, was released. He was married on 26 October 1961 to Jennifer June Lushington Cooper, daughter of
Derek Cooper. Lady Sligo is the stepdaughter of the former
Viscountess Ruthven of Canberra, and her father became in 1952 the stepfather of two young stepsons, now the late
Earl of Gowrie and his brother the journalist and Islamic scholar
Malise Ruthven. The Marquess and Marchioness had five daughters. After his death, his daughters inherited the family estate of Westport while his cousin
Sebastian Browne succeeded him as Marquess. Lord Sligo introduced a private members' Bill in
Dáil Éireann in 1990 to allow the dissolution of a family trust which would prevent his five daughters from inheriting Westport House due to their
female gender. ==Arms==