London - Sinn Fein signalled a shift to a new, post-conflict generation in Northern Ireland on Monday when the Irish republican party named a 40-year-old woman to replace a former IRA commander as its leader in Belfast.Michelle O'Neill will be a candidate to replace Martin McGuinness as deputy first minister after elections on March 2, following his decision to quit politics for health reasons.At a press conference in Belfast, Sinn Fein president Gerry Adams described O'Neill as the "new generation" who would "continue the good work Martin pioneered".O'Neill, a member of the Northern Ireland assembly for the past 10 years, developed her political career in the aftermath of the 1998 Good Friday peace agreement.The deal effectively ended the armed campaign by the paramilitary Irish Republican Army - in which McGuinness served - to unite Ireland by force.Yet O'Neill, a mother of two grown-up children originally from Clonoe in rural County Tyrone, also has a strong Irish nationalist background.Her father Basil served a prison sentence for IRA activities and her cousin Tony Doris, an IRA combatant, was killed by the British army in an ambush in 1991. In a video statement, O'Neil expressed her "immense pride" at her nomination and paid tribute to her father and cousin, citing the influence they had on her and on her wider community.She also offered an olive branch of sorts to the unionist community, which wants Northern Ireland to remain a British province.Place for everybody"The united Ireland we want and which we envisage has a place for everybody," she said. "I see it as my job as leader to make sure we are reaching out to all sections of the community.... Nobody has anything to fear."During the three-decade-long conflict known as "the Troubles", in which 3,500 people died, Sinn Fein was regarded as the political wing of the IRA.It has had an fractious relationship with unionists in the power-sharing assembly set up as part of the peace agreement.McGuinness played a key role in the peace process and served for a decade alongside first ministers from the Democratic Unionist Party (DUP).But he fell out with its latest leader, Arlene Foster, and resigned earlier this month, triggering new elections.The DUP responded to Sinn Fein's announcement by posting a tweet picturing Adams with O'Neill in his pocket, with the words: "New Deputy. Same Problem."