McKeown was born in 1956 in Randalstown, County Antrim, Northern Ireland. As a teenager, McKeown had ambitions of becoming an architect and when aged 16 he started working in the offices of a quantity surveyor. When aged 17 he joined the IRA, and he was arrested in August 1976 and charged with causing explosions and the attempted murder of a member of the Royal Ulster Constabulary. At his trial in April 1977, McKeown was found guilty and sentenced to life imprisonment in the Maze Prison.
While in prison McKeown took part in the blanket and dirty protests attempting to secure the return of Special Category Status for convicted paramilitary prisoners. In late 1980 the protest escalated and seven prisoners took part in a fifty-three-day hunger strike, aimed at restoring political status by securing what were known as the "Five Demands":
The right to one visit, one letter and one parcel per week;
Full restoration of remission lost through the protest.
The strike ended before any prisoners had died and without political status being secured, and a second hunger strike began on 1 March 1981 led by Bobby Sands, the IRA's former Officer Commanding in the prison. McKeown joined the strike on 29 June, after Sands and three other prisoners had died. Following the deaths of six other prisoners, McKeown's family authorised medical intervention to save his life on 6 September, the 70th day of his hunger strike. He described his recollection of the events in an interview:
You're very sleepy and very, very tired and you're sort of nodding off to sleep but something's telling you to keep waking up. This was the thing that kept everybody going through the hunger strike in trying to live or last out as long as possible. I knew death was close but I wasn't afraid to die – and it wasn't any sort of courageous or glorious thing. I think death would have been a release. You can never feel that way again. It's not like tiredness. It's an absolute, total, mental and physical exhaustion. It's literally like slipping into death.
Freedom
McKeown completed a bachelor's degree in social science from the Open University while in prison before being released in 1992, and subsequently obtained a PhD in Sociology from Queen's University Belfast. In the mid-1990s he co-founded the Belfast Film Festival, and has written two books about Irish republican prisoners in the Maze Prison; Nor Meekly Serve My Time: The H-Block Struggle 1976–1981 was published in 1994, and Out Of Time: Irish Republican Prisoners, Long Kesh, 1972–2000 was published in 2001. McKeown and Brian Campbell co-wrote a film about the 1981 hunger strike called H3 which was directed by Les Blair, and premiered in cinemas on 28 September 2001. Before the death of Campbell in 2005, he and McKeown also wrote two plays together, The Laughter of Our Children which debuted in 2001, and A Cold House which debuted in 2003. McKeown's first solo play, The Official Version, debuted on 18 September 2006. In 2006 he appeared in a two-part documentary titled Hunger Strike, which was shown on RTÉ to mark the 25th anniversary of the 1981 hunger strike. McKeown also works as a Development Officer for Coiste na nIarchimí, an umbrella organisation of republican ex-prisoners groups. In 1996 he was an unsuccessful candidate in the Northern Ireland Forum election in South Antrim.