A mother has helplessly watched two of her children die in a horrific car crash

A mother has helplessly watched two of her children die in a horrific car crash after her boyfriend veered into oncoming traffic as she drove in a car behind them.

Erin Sanderson and two of her children were in a rental truck trailing her boyfriend's Mustang, which was carrying her three other children, as they moved from Texas to Missouri on Sunday.

But on U.S. 60 in Oklahoma, her boyfriend, 39-year-old Willis George, turned into oncoming traffic, smashing into a pickup travelling in the opposite direction.

George and two of Sanderson's children, 14-year-old Drake Cobb and 13-year-old Syrrena Sanderson, died in the crash as their horrified mother and siblings looked on.

The other child in the Mustang, seven-year-old Maryssa Sanderson, survived with two broken legs and remains in hospital in Springfield, Oklahoma in serious but stable condition.