Kenneth Johnson, of Eagle, is now facing three class-three felony manslaughter charges.
The Clay County accident killed a Hastings couple, 53-year-old Gary Isom and 52-year-old Susan Isom, when their SUV was struck by the semi driven by Johnson.
Their daughter, 26-year-old Tiffany Isom, died several days after the collision. Her 16-year-old brother was also injured in the accident.
Authorities say Johnson failed to heed a stop sign at the intersection of U.S. Highway 6 and Nebraska Highway 14 near Saronville. The accident occurred early Thursday morning.