He was the son of Irish immigrants Mary (née Waters) and Nicholas John Kirwan.

His father was a "gentleman farmer" originally from County Galway, while his mother was the granddaughter of Garrett Byrne of Ballymanus, a leader of the Irish Rebellion of 1798.

[1] At first, he continued writing in Brisbane, Melbourne and South Australian newspapers but moved to Kalgoorlie in 1895, attracted by the great gold discoveries.

Following its defeat in 1916, he worked with governments of both major political persuasions and strongly advocated for his Goldfields constituency.

In 1912, he married Teresa Gertrude Quinlan, the daughter of politician Timothy Quinlan, and they had three sons (a twin male having died at birth), two grandchildren (a boy and a girl) and three great grandchildren (a girl and two boys).