Joe Biden’s interest in Brexit’s Irish Sea trade border should come as little surprise given the US President’s deep affection for his ancestral home.

Paraphrasing James Joyce, one of his favourite Irish writers, Mr Biden once wrote that north-east Pennsylvania would be written on his heart when he dies but “Ireland will be written on my soul”.

His Irish Catholic heritage is not only a source of intense pride but it also frames much of his political backstory.

The number of times Joyce and other Irish literary greats, such as Seamus Heaney and William Butler Yeats, find their way into his speeches is apparently somewhat of a running joke in Washington DC.

Fifth cousins of Joe Biden, councillor Andrea McKevitt, left, and her sister Ciara, from Co Louth celebrating the US president's inauguration earlier this year
Fifth cousins of Joe Biden, councillor Andrea McKevitt, left, and her sister Ciara, from Co Louth celebrating the US president’s inauguration earlier this year (Brian Lawless/PA)

Mr Biden is also fond of quoting Irish phrases and sayings that have been handed down through generations of his family.

During the election campaign last year when a BBC reporter tried to grab a quick word with the Democratic candidate, he quipped back: “The BBC? I’m Irish.”

Unionists in Northern Ireland would see him as overly sympathetic to the nationalist perspective.

This perception was reinforced with a joke he made outside his vice presidential residence in Washington during the St Patrick’s festivities in 2015.

Greeting then taoiseach Enda Kenny at the front door he told the assembled media pack “anyone wearing orange is not welcome in here”.

He hastily added “only joking”, but it was a one-liner that did not go down well with members of the unionist community back on the other side of the Atlantic.

Enda Kenny and Joe Biden
Mr Biden, right, with former taoiseach Enda Kenny

They view his interventions on Brexit in the same context, accusing him of being too willing to accept the narrative from the EU and Irish Government that the NI Protocol is required to preserve stability and peace on the island.

Unionists and loyalists believe directly the opposite – that it is the protocol itself, and the barriers it has created between Northern Ireland and the rest of the UK, which is causing the instability.

Mr Biden can trace his ancestry to Ireland’s west and east coasts, specifically Ballina in Co Mayo and the Cooley Peninsula in Co Louth.

His great great-grandfather Owen Finnegan emigrated to the United States from the Cooley peninsula while another great, great-grandfather Patrick Blewitt was born in Ballina, leaving during the Irish famine in 1850 to sail to America.

Distant relatives celebrated his election win in both areas back in November and gathered again in January to mark his inauguration.

Champagne corks were popped, cakes were baked and a huge mural of the 46th president was even painted on a wall in Ballina.

The affection is reciprocated and Mr Biden has visited both counties in recent years to meet long lost cousins.

There are few sure things in politics but a return visit to Ireland by the now President Biden seems a fairly certain bet.