The boy, from Leicester, was pronounced dead at the scene after a lorry smashed into a Toyota Yaris which is thought to have been parked on the hard shoulder.
A man believed to be in his 60s and a woman, thought to be in her 20s, were also in the car at the time of the crash at roughly 7.30pm on Thursday.
The man was treated for a suspected fractured shoulder at the scene while the woman was treated for a leg injury.
They were both taken to Birmingham Heartlands Hospital with serious injuries.
Police have arrested a 62-year-old lorry driver from Hampshire on suspicion of causing death by dangerous driving.
He was unharmed in the collision.
The motorway was closed between junctions 6 and 5 southbound for several hours after the collision.
#M6 Junction 6 Southbound #Birmingham closed due to accident, Ambulance and Police cars in scene! Expected Road opening 22.00 Hope everyone will be ok #EMAS proving their everyday awesome work! 🚑 pic.twitter.com/9ZqlxY1ezb
— Claire Maynard (@ClaireM85) May 31, 2018
A West Midlands Ambulance Service spokesman said: “Crews arrived to find three patients, all of whom had been travelling in the car.
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“The boy was found to be in cardiac arrest and ambulance staff immediately began CPR.
“Unfortunately, it quickly became apparent nothing could be done to save him and he was confirmed dead at the scene.”