Mother Saadia Ahmad (37) was pronounced dead at the scene, while her nine-year-old daughter Ayesha died in hospital on Saturday,
Three other members of the family - the father, also aged 37, and two young sons, aged ten and 14 - are still in hospital in a serious but stable condition.
The accident occured around 9pm when a silver Mercedes car and a white Vauxhall van collided on a stretch of the M9 between Polmont and Linlithgow.
A 42 year old man, the driver of the other vehicle, also died following the collision.
Police Scotland have appealed for anyone who may have witnessed the crash to call 101.