FACTBOX-Facts about N.Ireland's Martin McGuinness

(Reuters) - Martin McGuinness, a leading member of Irish nationalist party Sinn Fein, is expected to become Deputy First Minister of Northern Ireland on May 8 after a deal between the province's main Protestant and Catholic parties on Monday.

Here are some facts about McGuinness:

* Born in Londonderry in May 1950, McGuinness joined the Irish Republican Army at the age of 20 as the guerrilla group began its 30-year campaign against British rule in Northern Ireland, swiftly rising through the ranks to become a senior commander.

* Along with party leader Gerry Adams, he was instrumental in transforming the IRA's political ally Sinn Fein from a down-at-heel lobby group into Northern Ireland's most powerful nationalist grouping.

* He became Sinn Fein's chief negotiator in the early 1990s and played a key role in talks that led to 1998's Good Friday Agreement to end conflict between majority Protestants committed to ties with Britain and a Roman Catholic minority in favor of a united Ireland.

* In 1997 he was elected to the British parliament but like party colleagues refused to take his seat at Westminster where he would have had to swear an oath of allegiance to the British crown. He served as education minister in the last, short-lived Belfast Assembly.

* He dismissed as "absolute nonsense" allegations in 2006 in an Irish tabloid newspaper that he had worked for Britain's MI6 intelligence service. The report followed revelations that another party veteran had been a long-serving British agent.