The son and daughter of the Northern Ireland rally driver, Bertie Fisher, were killed and Mr Fisher, his wife, Gladys, and another son critically injured in a helicopter crash in Co Fermanagh yesterday.
A spokesman for the Northern Ireland Ambulance Service said Mark (27) and Emma (25) died at the scene of the crash, which was reported at 3.25 p.m.
Mr Fisher is known to be an accomplished pilot, and the helicopter was his.
A statement from the Erne Hospital, Enniskillen, last night said Mrs Fisher was being transferred from there to the Royal Victoria Hospital in Belfast. Their 23-year-old son was being taken to Altnagelvin Hospital, Derry, and Mr Fisher was remaining in the intensive care unit at the Erne Hospital.
Two of the three were said to be in a critical condition; the other was described as stable.
The family home is seven miles from the crash site, across Upper Lough Erne, in Ballinamallard, Co Fermanagh.
Mr Kenny McMahon, director of operations for the ambulance service, said four ambulances were dispatched to the scene at Monea, five miles outside Enniskillen, but found the terrain very difficult.
The three surviving occupants of the aircraft were taken by a British army helicopter to the Erne Hospital.
Locals said Mr Fisher's helicopter was a common sight around Fermanagh and he used it to travel to business and rally fixtures. It is understood the family were returning home after a weekend in the west of Ireland.
Mark Fisher, like his father, was a leading rally driver.
The North's Environment Minister, Mr Sam Foster, who knows the Fisher family, said they were known and respected in the Fermanagh community. "I am devastated and would like to express from the people of Fermanagh-South Tyrone my sincere sympathy to the family."
Helicopter crashes are comparatively rare in Ireland. In 1999 four Air Corps personnel were killed when the rotor blades on their Dauphin helicopter came into contact with a sand dune in Co Waterford.
In 1996 three English pilots died when a Sikorsky SK76 helicopter crashed into a mountain in Co Louth.