Jane Baker-Lockett, 43 and James and Amy Gaskin, 12, died in a collision on the A361 in north Devon
The crash was believed to have been witnessed by Jane Baker-Lockett's husband, stepfather to James and Amy, who was in a separate vehicle with their 14-year-old son.
Baker-Lockett was pronounced dead at the scene, Amy was pronounced dead on arrival to the hospital and her brother, James, died shortly after arriving.
Emergency services were called at 8.25am on Monday, closing the road for nine hours while officers from the Exeter serious collision investigation unit examined the scene.
Insp Richard McLellan, of Devon and Cornwall police, said: “It would seem that a car travelling towards Barnstaple, for unknown reasons at the moment, has crossed the centre white line and hit an oncoming truck.
“Unfortunately the family were travelling in two separate cars but travelling together along this road so the dad was there at the scene as well.”
Officers are appealing for witnesses to the crash.
