A one-vehicle rollover crash Friday afternoon threw all six people from the SUV, killing the two adults.
All of those involved are from Unionville, Mo.
The crash happened at 2:30 p.m. on Highway 136 in Putnam County one mile east of Hartford.
Killed in the crash were Barry Maddox, 35, and Stacey Gooden, 28.
The Missouri State Highway Patrol reported that a Ford Excursion driven by Maddox crossed the center line.
Investigators said Maddox overcorrected and ran off the right side of the highway.
The SUV overturned several times, ejecting all occupants.
Gooden was pronounced dead at the scene by the Putnam County coroner.
Maddox was pronounced dead on arrival at Mercy Hospital in Centerville, where he was taken by an Air Evac helicopter.
Maddox's seven-year-old twin sons, Tristan and Triton, suffered moderate injuries.
Both boys were taken by ambulance to Northeast Regional Medical Center.
Gooden's two children, Cason Barker, 10, and Jessilena Barker, 2, suffered serious injuries.
Cason was flown by Air Evac to Iowa Methodist Hospital in Des Moines.
Jessilena was taken by ambulance to Northeast Regional Medical Center.