Saadia Ahmad, 37, and her nine-year-old daughter Ayesha Ahmad, died following the collision between a van and the car they were travelling in on the M9 in West Lothian at around 9pm on Friday.
Three other members of the family - the father, also 37, and two sons, aged 10 and 14 - were on Sunday night still in hospital in a serious but stable condition. They were being treated at the Forth Valley Royal Hospital and the Queen Elizabeth University Hospital in Glasgow.
A 42-year-old man, the driver of the van, was pronounced dead at the scene. He has not yet been named by police.
The collision happened on the southbound carriageway between Polmont and Linlithgow and involved a silver Mercedes car and a white Vauxhall van.
Police have asked any witnesses to contact officers.