The June 2003 fire killed 9-year-old Manuel Fuentes III and his 13-year-old sister, Lauren.
Their parents, Manuel Jr. and Terrie Fuentes, were badly burned.
The lawsuit, filed in Morrill County District Court, alleges that landlord Shirley Rittenhouse and 10 other unnamed defendants were negligent for not installing smoke detectors in the home.
Rittenhouse did not immediately return a telephone call to his home seeking comment.
State fire investigators said a smoldering cigarette or hot ember from a cigarette probably caused the fire.
The fire apparently spread from a smoldering burn between a cushion and an arm rest on an upholstered chair in an enclosed porch, Deputy State Fire Marshal Mike Turner said at the time.
The family's two other children _ Jessica and Julia, who were 9 and 6 years old at the time _ were treated for minor injuries after the fire.
Terrie Fuentes told neighbors immediately after the fire that she had all three of her daughters with her inside the house at one point, but Lauren wouldn't run through the flames to escape.
Manuel Fuentes Jr. had to be physically restrained by a police officer to keep him from going back into the burning house to get his children.
The children were later found dead in a closet, where they had sought refuge from the fire.
The lawsuit, which asks for unspecified damages, was filed by attorneys Maren Chalouopka of Scottsbluff and Charles Richardson of Tulsa, Okla.
