There are claims that the injuries suffered by Harry Dunn were not considered life-threatening by emergency call handlers, despite "breaking every major bone" in a collision described as a "crash fireball".
The 19-year-old was forced to wait for paramedics for 43 minutes after the emergency call was "wrongly categorised" the family's spokesman said.
Mr Dunn's family met with chief executive of East Midlands Ambulance Service Richard Henderson and director of quality Nichola Bramhall to discuss the delay.
The family's spokesman Radd Seiger said Harry's parents, Charlotte Charles and Tim Dunn, are "full of praise" for the work of the paramedics on the scene, but said the delay in getting to their son was "worrying".
The family are currently pursuing a civil claim for damages which could be worth "millions of dollars" against the suspect in the case, 42-year-old Anne Sacoolas, after she was granted diplomatic immunity in the days following the crash.
It's understood that the first call made by a witness to the collision was put in category two, which are incidents of a potentially serious condition, by ambulance staff - which estimates a waiting time of 40 minutes for patients.
If the teenager's condition was considered as category one, which is described as life-threatening and needing immediate intervention, ambulance crews should aim to attend in seven minutes under NHS England guidelines.
Despite being wrongly categorised, Mr Seiger says the delay would have been the same regardless because all 22 crews stationed in Northamptonshire were on other calls.