Police officials said the accident happened near Wattganj village under Piprakothi police station of the district.
Piprakothi Station House Officer Sanjeev Kumar said that the family was going to Kotwa in East Champaran from Muzaffarpur when it lost control and dashed into the container carrier.
All the deceased are in twenties and early thirties. The SHO said they were residents of Pokhra village under Kotwa police station of East Champaran. The injured kids have been admitted to Motihari Sadar Hospital.