Mr McGuinness, as Sinn Fein's chief negotiator during the Northern Ireland peace process, has long been a public face of the republican movement. Bairbre de Brun, meanwhile, is a comparatively new member on the Sinn Fein frontbench.

Since the 1970s, Mr McGuinness has been a powerful advocate of Irish republicanism.

His initial inspiration to become involved in politics sprang from an interview for a mechanic's position, which ended abruptly when he said he was a Catholic.

Stormont will be the seat of the new executive

In 1970s Londonderry, such religious discrimination was commonplace.

Another formative influence on Mr McGuinness was the arrival of British soldiers on the Bogside.

He later wrote: "Those chiefly responsible for the corruption of Irish life were the British; it was they who had established and underpinned the northern state; it was they who had stood idly by through fifty years of blatant injustice, discrimination and inequality."

He has consistently denied that he played a leading role in the IRA in Londonderry. He has been described by Ken Maginnis of the Ulster Unionist Party as the "capo di tutti capi" - the godfather of all godfathers.

His first took to the centre stage of politics in July 1972 when along with Gerry Adams he met the then Secretary of State for Northern Ireland, William Whitelaw.

Martin McGuinness's political education took place in Londonderry

He and Mr Adams were the principal architects of Sinn Fein's move into the political mainstream.

In 1986, at the Sinn Fein annual conference, they spearheaded a move to recognise the Irish Parliament in Dublin, a radical shift in republican thinking which led to the then Sinn Fein leader, Ruairi O Bradaigh walking out to form Republican Sinn Fein.

Since 1986, Mr McGuinness has been involved in a number of key negotiations which have characterised Sinn Fein's move towards their current position.

Most importantly, he and convicted IRA bomber and Maze escapee Gerry Kelly were having secret talks with British officials at a time when then Prime Minister John Major was declaring in the Commons that to have talks with Sinn Fein would make him sick to his stomach.

Gerry Adams and Martin McGuinness have long been political allies

Those talks led to the Downing Street Declaration in December 1993 and the first IRA ceasefire in August 1994.

As well as being an assembly member and likely minister, Mr McGuinness is a non-sitting MP for Mid Ulster and is Sinn Fein's representative dealing with General Jean de Chastelain's Decommissioning Body.

He has been imprisoned on a number of occasions, both in Northern Ireland and the Republic. In between his spells in prison, he married Bernie Canning.

Mr McGuinness strives to keep his private life private although he did let his guard slip at Hillsborough this Easter when, in the midst of what were trying political times, Gerry Adams took time out to congratulate him publicly for becoming a grandfather.

De Brun: Feared for toughness

Little is known about Bairbre de Brun before she came to prominence as one of Sinn Fein's toughest negotiators in the recent Stormont Talks.

A native of Dublin with family links to Belfast and a school teacher by profession, she has been active in republican circles for almost 20 years though not always a member of Sinn Fein.

She is being touted as a possible minister for education in the new administration, if and when it comes about, because of her teaching background but she has not ruled out other portfolios either.

Her current role as justice and policing spokesperson emphasises that she is able to get on top of other briefs.

She has a reputation as being a hard worker with a keen intelligence. Her media profile has increased considerably since the talks which led to the Good Friday Agreement.

Her toughness is reputed to be as feared both inside and outside her own party.

A keen Irish speaker, she is also proficient in a number of other languages including French.

But true to Sinn Fein form she keeps her private life very much to herself.

Unmarried, she is reluctant to release any details of her personal life, even her age - though she is reckoned to be in her early 40s.

Prior to her election as assembly member for West Belfast, she held a number of senior positions within Sinn Fein.

She was involved in the party's International Affairs department and in its Cultural section before that.

Her first involvement with the republican movement came in the beginning of the 1980s when she was associated with the National H-Blocks / Armagh Committee, a group which campaigned for the hunger strikers in the Maze and Armagh prisons.

At that time, she was not a member of Sinn Fein though she did join the party later in the 1980s.