 He was a member of the House of Representatives for over 35 years (1911–1931, 1934–1949), one of the longest periods of service.His brother Tom Brennan was a United Australia Party senator, a rare instance of family members representing opposing parties.Brennan was born at Upper Emu Creek near Bendigo, Victoria and was a younger brother of Tom Brennan, later an assistant minister in the conservative Lyons government.