The former Wings guitarist Henry McCullough is critically ill following a heart attack.
Mr McCullough, from Portstewart, County Derry, and who is a frequent visitor to Donegal and has spent much time in Ramelton, is one of the best known guitarists in the world, performing with a host of legendary artists.
Mr McCullough is being treated at the Causeway Hospital in Coleraine.
A spokeswoman for the hospital said he was in a "critical condition".
The rock guitarist played with Beatles star Paul McCartney in Wings, before embarking on a successful solo career.
He is perhaps best known for his playing on Wings' number one hit My Love, but he also performed with Joe Cocker at the famous Woodstock festival in 1969.
His sister Rae Morrison said the family were very distressed.
He was invited by the Beatle Paul McCartney to join Wings in the 1970s and spent 18 months touring with them.
Despite early reports that he had died, his sister Rae Morrison said he was still battling.
She said he had suffered a heart attack on Monday and the family are worried and distressed but that they had been inundated with messages of support.
"He is a very special person," she said.
"We really are very worried for him, his sister is on her way home from Florida and his brother is coming home from Glasgow."
Mr McCullough, who is 69, was also a member of Joe Cocker's band.
He played with Cocker at the legendary Woodstock concert in 1969, the only Irishman to perform there.
McCullough spent 18 months touring and recording with Wings in the 1970s, after being invited to join the band following a number of jamming sessions with McCartney.
He has been hailed for his guitar work on the US number one hit My Love.
McCullough later signed to the Dark Horse record label of another Beatle, George Harrison, for his solo album Mind Your Own Business.