Brooke, Sir Arthur (1726–85), landowner and MP, was elder son of Henry Brooke of Colebrooke, Co. Fermanagh, MP for Fermanagh, and his wife Lettice (Letitia), daughter of Benjamin Burton (qv) of Dublin. Arthur Brooke succeeded his father in the estate and as MP for the county in 1761, and also inherited properties in Dublin and elsewhere from his great-uncle, Arthur Cole, Viscount Ranelagh. In 1774 he voted for catholic relief, and in 1775 wrote a pamphlet suggesting that property-owning catholics, in order to secure public office and consolidate their status in society, would eventually wish to turn protestant. He encouraged the development of the linen industry in his area, was a trustee (1763–85) of the linen board, and was made a baronet (1764) and a privy counsellor (1767).
He married (1751) Margaret Fortescue, sister of Lord Clermont, but his family's status and political interest suffered from his ruinous extravagance, his gambling, and his wavering support for the government. For the same reasons, he failed to secure a peerage and lost his seat in parliament (1783), though his son-in-law Sir John Parnell (qv) secured his election the same year for Maryborough. He was a Volunteer colonel and a delegate for Co. Fermanagh to the national Volunteer convention held in Dublin (1783).
At his death (7 March 1785) the family estates were much reduced and burdened with debt, and the baronetcy became extinct. One of his daughters married Thomas Vesey, later 1st Viscount de Vesci; the other, wife of Sir John Parnell, was ancestor of Charles Stewart Parnell (qv). A son died young; an illegitimate son became a postillion at Colebrooke.