The pop star's uncle Seamus Horan passed away last Thursday in the care of doctors, nurses and staff at the Midland Regional Hospital in Niall's hometown of Mullingar.
"Seamus was in poor health for a good few years," Mullingar councillor Michael Dollard told the Herald. "He was the brother of Bobby – Niall's father – and a great man."
Before his health began to fail him, Seamus was a top- class sprinter. "He was a real gentleman and a brilliant sprinter," Michael said.
"He was a fantastic athlete. He was part of the Mullingar Harriers Athletic Club. He was a brilliant runner and a Labour man – he'll definitely be missed."
Seamus spent 20 years living in the US and his daughter Katie is still based there.
His funeral took place yesterday afternoon in the Cathedral of Christ the King and many members of the community attended and paid their respects to Seamus, also known as Jim.
"There was a great turn- out at the funeral," Michael added.