AUSTIN (KXAN) – The family involved in a deadly crash near Liberty Hill is now suing the maker of their car.

In late April, a suspected drunk driver slammed into the back of Crystal Draper’s Nissan Altima as she waited to make a left turn off U.S. Highway 183 into their neighborhood. Two of her children, 10-year-old Kirsten, and 15-year-old Koby, were killed in the crash.

The family is suing the Nissan, claiming its design contributed to the deaths of the two children. The suit states the Nissan Altima was equipped with “inadequate occupant protection systems,” presumably referring to the seat belts. Crystal and her two other children, Kristopher and Kody, were badly injured in the crash. The lawsuit claims product liability, gross negligence and wrongful death, given the two children died despite wearing seat belts.

“There were safer alternative designs to eliminate or significantly reduce the possibility of the catastrophic injury or death,” the document says.

The suit goes on to say the automaker “did not adequately design the Nissan Altima” and “did not adequately test to determine whether design and marketing defects existed.”

The eight-page lawsuit does not specify how much the family is seeking in damages.

The man accused of hitting the Draper family, John Alvarado, remains in the Williamson County Jail. Investigators said he was drunk at the time of the crash. He had previously been charged with intoxication manslaughter, but online jail records show he now faces two counts of first-degree murder and three counts aggravated assault with a deadly weapon. He is due in court again in July.