The boys were aged 4 and 10. The driver of the car, believed to be the boy's mother, and another female passenger, remain in a stable condition in hospital.
The crash occurred on the northbound carriageway near junction 15 at around 11.25am this morning.
The motorway has now reopened.
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Mainly dry with variable cloud and a lighter breeze. Feeling a little warmer in any sunny breaks. Higher risk of showers towards evening
Showers dying away overnight. Chilly start but mainly dry on Friday.