Hazel Gibson's boyfriend Michael Joyce, 31, and her seven-year-old son Cole Gibson were killed when the car she was driving was involved in a head-on collision.
Ms Gibson, 31, from Lochgelly in Fife, was pregnant at the time of the crash on the A9 in Perthshire in November 2011. She suffered serious injuries and was rushed to hospital with pelvic fractures, broken ribs and a fractured spine.
But the parents of Mr Joyce, from Edinburgh, and other family members launched a legal action against her and her insurers at the Court of Session. They claimed she had lost control of the vehicle and caused it to swerve into the opposite lane where it crashed into an oncoming Peugeot 206.
In court, Ms Gibson's lawyers blamed Mr Joyce for the crash, and claimed he had grabbed the steering wheel causing the car to veer across the carriageway.
In a judgment published yesterday, Lord Kinclaven ruled that Ms Gibson had been at fault and awarded damages totalling £185,000 to six relatives of Mr Joyce.
He said: "Clearly, this is a tragic case for all concerned. I have given anxious consideration to the evidence and to everything said [on behalf of the defenders and on behalf of the pursuers]. I have reached the conclusion that the pursuers are entitled to reparation from the defenders.
"On the evidence, the defenders have failed to provide an acceptable non-negligent account of how the accident occurred. I was not satisfied by the first defender's explanation. It follows that the agreed presumption of negligence applies."
Mr Joyce, who was not Cole's father, was declared dead by paramedics at the scene.
Cole, who was sitting in a back seat of the car, died at Ninewells Hospital in Dundee a few days later.
Mr Joyce's family claimed Ms Gibson had changed her story several times about the circumstances of the accident.
At one stage she posted a Facebook message saying her partner was a "hero" as he had sacrificed himself to save her and her unborn child.
Accident investigators told the court the accident was likely to have been caused by Ms Gibson initially swerving to the left and then overcorrecting to the right.
Speaking shortly after the tragedy, Ms Gibson told how she had taken comfort from the fact Cole's organs had been donated to help other youngsters.
Her son had decided he wanted to be on the donor register at the age of five after picking up a leaflet that had come through the family's letterbox.
She said at the time: "Knowing that Cole's death is helping other children waiting for transplants is helping me in some way to come to terms with what has happened.
"I already know that his heart is going to a two-year-old girl and that has given me a glimmer of hope knowing that, although he is not here, he's making a difference to a very sick young girl elsewhere in the UK."
Miss Gibson added that it had been a "miracle" she had not miscarried as a result of the accident.
She said: "I can only think that wearing a special pregnancy bump seat belt helped in some way, although I can never be sure."
Five months after the accident she gave birth to a son.