Police have named the two brothers and a 32-year-old woman who were killed when the car they were travelling in flipped over on the M6 on Christmas Day.
Brothers Adnan Habib, 10, and Mohammed Arsalaan Habib, 4, and Bushra Tazarib were travelling to a family wedding in the Greater Manchester region when they died.
All three victims were from High Wycombe in Buckinghamshire.
The car's two other occupants, including the boys' mother who was driving, survived the crash, which happened near junction 15, close to Stoke-on-Trent, at 11.25am.
The mother of the boys and the other passenger, a female relative, spent the night at the University Hospital of North Staffordshire in a stable condition. They were discharged on Boxing Day.
Officers continued to appeal to the public for help to work out exactly what happened when the red Ford Focus crashed.
The police force said it was described by investigating officers as "unimaginably sad and tragic".
Chief Superintendent Martin Evans of the Central Motorway Policing Group (CMPG) said: "The thoughts of all officers and emergency services colleagues involved are with the bereaved families at this extremely difficult time, and specially trained family liaison officers have been appointed to support them."
The crash shut the M6 for much of the day to allow emergency services - including three ambulances and two air ambulances - to reach the scene.
No other vehicles were believed to have been involved and the circumstances surrounding what caused the crash are being investigated by the CMPG.
:: Anyone with information about the crash is urged to contact the force's collision investigation unit on 01785 234094.