The former leader of the Democratic Unionist party (DUP) Dr Ian Paisley has died aged 88, his widow said.

The firebrand preacher-turned-politician died on Friday morning, according to Eileen Paisley, a fellow member of the House of Lords.

She said the family was heartbroken by the death of a figure who dominated Ulster Unionist politics for nearly six decades.

In a statement released by the Paisley family at lunchtime on Friday, she said: "My beloved husband, Ian, entered his eternal rest this morning. Although ours is the grand hope of reunion, naturally as a family we are heartbroken. We loved him and he adored us, and our earthly lives are forever changed."

Paisley, or Lord Bannside as he was known in his latter years, embarked on a remarkable political journey that started with him opposing mild reforms to the unionist-dominated Northern Ireland state in the late 1950s and early 60s to sharing power with his one-time mortal enemies Sinn Féin in the 21st century.

The 88-year-old founder of the fundamentalist Free Presbyterian Church moved from being Ulster's "Dr No", who rejected political compromises with nationalists during the height of the Northern Ireland Troubles to ultimately getting into government with Sinn Féin after the 2006 St Andrews Agreement.

Ian Paisley entering the DUP office in Ballymena as he prepared to announce his retirement from the British Parliament in March 2010. Photograph: AFP/Getty Images

His hardline brand of politics saw off a succession of modernising unionist leaders, from prime minister Terence O'Neill in the 1960s to Nobel peace prize winner David Trimble in 2005. But after fulfilling his dream in 2005 of becoming the dominant force in unionism, Paisley finally agreed to share power with Sinn Féin, the party he vowed to smash in the 1980s.

One of the most surprising developments in the latter years of his career was how he forged a warm relationship with Martin McGuinness, Sinn Féin's deputy first minister of Northern Ireland and one-time IRA chief of staff. Due to the fact that the unlikely couple running Northern Ireland were pictured almost always smiling together, the pair earned the nickname "the Chuckle Brothers".

McGuiness paid tribute to Paisley on Twitter: "Very sad to learn that Ian Paisley has died. My deepest sympathy to his wife Eileen & family. Once political opponents – I have lost a friend."

Martin McGuinness and Ian Paisley in Dundalk. Photograph: Paul Faith/PA

In her statement, Eileen Paisley said that the funeral would be private and attended only by the immediate family.

She added: "As a family we appreciate that there will be an expectation by those who admired him to express their gratitude for his life and their sorrow at his passing.

"To that end we will in due course publish details of a public memorial service which, will be scheduled later in the year.

Lord Bannside, who held the Westminster seat of North Antrim for decades, handed over the constituency to his son Ian Paisley Jr, who still represents the Paisley heartland in the House of Commons.