America has turned down an extradition request for the woman charged over the death of Harry Dunn.
Family spokesman Radd Seiger said that US Secretary of State Mike Pompeo denied the request.
Harry, 19, died in a head-on crash with a car in August last year near to RAF Croughton in Northamptonshire.
The driver of the car, Anne Sacoolas, the 42-year-old wife of a US spy, claimed diplomatic immunity and returned to America, where she has been since Harry died.
Seiger, said their constituency MP Andrea Leadsom informed them of the news that the extradition request had been turned down.
Leadsom is due to meet the US ambassador Woody Johnson in London on Friday to discuss the case.
Seiger said the family were taking time to process the news and would be reacting fully on Friday morning.
Boris Johnson has previously described the chances of the US handing her over as “very low”.
She returned to the US after the crash and is claiming diplomatic immunity.
Despite police charging her with causing death by dangerous driving her lawyer has said she will not return to the UK voluntarily.
