Liam Dearie, from Dundonald, near Kilmarnock in Ayrshire, was struck by a 4x4 as he headed to a shop in the village with a friend and an adult on Monday.
His death is the second tragedy in a year for his family, as his father died suddenly in his sleep last May. He lived with his mother Jane and sister Shannon.
Liam suffered serious head injuries and broken ribs in the accident in Main Road, at 4:20pm. He was taken by ambulance to Crosshouse Hospital in Kilmarnock. He was then transferred to the Southern General hospital in Glasgow where he died on Monday evening.
The driver of the 4x4 was unhurt but "extremely shaken".
Last night neighbours said Liam's death had come less than a year after the sudden death of his father. Mr Dearie 43, was found dead in his bed by Jane, 34, in May 2009.
It is believed Mr Dearie had been suffering from respiratory problems and died during his sleep. Neighbour Rodney Cameron, 34, said: "I know the family pretty well and this is such a terrible tragedy. Liam's dad died suddenly last year in the house and for the family to have to go through this again is unbearable.
"Steven hadn't been keeping very well and had been suffering from respiratory problems," Mr Cameron said. "He was always at the doctor and was never really in the best of health.
"But his death came very suddenly and poor Jane found him lying in bed next to her.
"She tried to wake him up, but couldn't.
"They were a tight-knit family and no-one can believe this has happened to them again. Liam's death has shocked everyone here. The family are in bits."
One 65-year-old woman, who asked not to be named, yesterday said: "I was walking on the other side of the street when the accident happened.
"There was a loud bang and then all I could see was Liam lying on the ground. I've know him since he was a toddler. I couldn't believe it, it was a terrible sight."
One of the flower tributes placed at the scene read: "Liam we will miss your little smile and laughter. Sleep tight little man. You're now in the arms of the angels."
Sergeant Robbie Foster, of Ayr Road Policing Department, said: "We are continuing enquiries to establish the full circumstances of the crash. The area would have been busy and I would appeal to anyone who may have witnessed the crash to contact Ayr Road Policing. Alternatively, Crime-stoppers can be contacted where anonymity can be maintained."