 McWilliams was born on 15 December 1963 and grew up in staunchly republican west Belfast.His 16-year-old brother Paul, a member of the Provisional Irish Republican Army (IRA) youth section (Na Fianna), was shot dead by British Army soldiers in 1977 as he allegedly threw petrol bombs at their observation post during rioting in Ballymurphy.The following week McWilliams placed a death notice in the "Irish News" regarding his brother's death