During the Great Hunger of the 1840s, two men called Edward Blewitt and Owen Finnegan joined hundreds of thousands in fleeing Ireland for the United States
A century and a half later the great-great-great grandson of Blewitt and great-great grandson of Finnegan is the president of the United States.
Joe Biden is one of 34.7 million Americans who claim Irish heritage.
The president has maintained a keen interest in talks between the EU and UK over the Northern Ireland protocol which governs post-Brexit arrangements on the island of Ireland.
Here’s what Biden has said about his links to Derry and County Mayo.
What are Joe Biden’s ties to Ireland?
In 2016, then Vice President Joe Biden visited his ancestral home in Ballina, Co Mayo, meeting with long-lost cousins whose ancestors hadn’t taken the long and arduous trip across the Atlantic.
The White House contender is able to trace his roots to Derry and Louth, as well as Mayo.
Biden was born into a family of Irish-American Catholics in 1942, with Irish ancestors on both his mother and father’s side. US genealogist Megan Smolenyak believes Biden is “roughly five eighths” Irish.
His grandmother, Catherine Eugenia (Jean) Finnegan, who had a great influence on Biden, is descended from the Finnegan family in County Louth.
Smolenyak’s research suggests that Biden’s maternal great-great grandfather was Owen Finnegan who emigrated from Newry, County Down. Smolenyak noticed that Finnegan emigrated at the same time as one of former president Barack Obama’s ancestors.
"Owen Finnegan arrived in New York on May 31, 1849, just five weeks after Joseph Kearney, Obama's ancestor," Smolenyak writes on her website.
"Curiously, both men were shoemakers."
Biden’s great-great-great-grandfather, Edward Blewitt, emigrated from County Mayo in 1851.
His grandfather, Ambrose Finnegan, is believed to have emigrated from County Derry in the early 20th century. Finnegan was a textile worker, and it is believed he moved to the United States to work at a DuPont factory in Wilmington, Delaware.
What has Joe Biden said about Ireland?
Joe Biden has shown great pride in his connection to Ireland in the past, speaking candidly about his upbringing.
Speaking in 2016 he said, "I grew up in a household where my grandfather and grandmother Finnegan, all my mother's brothers and my father told us about the courage and commitment it took for our relatives to emigrate from Ireland - in the midst of tragedy - to distant shores where they didn't know what awaited them.
"And those values - their passion and principle, their faith and fortitude - shaped the way my siblings and I were raised."
Recalling his mother Jean Finnegan’s words in 2016, he said, "She would say: 'Remember Joey, you are defined by your courage, you are redeemed by your loyalty'. This is loyalty, man.”