He was one of the couple's youngest children, and his forename was a family name that honoured their Norman ancestor, Sir Hildebrand de Alington.
[1] He became an army officer, receiving a captain's commission from King James II of England in 1685.
[2] Hildebrand succeeded to the Irish title of 5th Baron Alington on 18 September 1691, on the death of his nephew, the 4th Baron, who had died without male issue; the English peerage became extinct.
[3][1] In 1700, he sold part of his estate, possibly anticipating the extinction of the title.
[4] He never married, though his elder brother William had urged him to,[4] and on his death the Irish Barony, Alington of Killard, also became extinct.