The tragedy happened when the silver Mitsubishi Shogun came off the A920 Colpy to Oldmeldrum road
The 74-year-old driver and his 60-year-old wife were seriously injured after the 4x4 careered into a tree on the Aberdeenshire road.
They were rushed to hospital where they remained in a critical condition yesterday.
The two sisters travelling in the back of the car were believed to be relatives of the couple. One of the women lived in Texas and the other comes from Gloucestershire.
Fire crews battled to cut the two elderly women free from the back of the car but they were pronounced dead at the scene.
The accident happened at about 4:10pm on Sunday during a spell of heavy rain which fell across the North-east.
A Police Scotland spokesman said: "At about 4.10 pm on Sunday 22 June 2014, Police, Fire and Ambulance attended a report of a one vehicle road traffic collision on the A920 Colpy to Oldmeldrum Road near Tocher.
"Tragically the two rear seat passengers, who were female, were pronounced dead at the scene.
"The female front seat passenger suffered multiple serious injuries and was conveyed to Aberdeen Royal Infirmary by ambulance where her condition is described as critical.
"The driver, who was male, also suffered multiple serious injuries and was conveyed to Aberdeen Royal Infirmary by ambulance."
The accident happened on a straight stretch of road near Meikle Wartle junction.