Brazoria County Fire Marshal Al Priselac said, "(The victim was) found in the back bedroom."
Three more family members were injured. The grandfather, Craig Eggleston, 59, was flown to the hospital.
"(He suffered) facial burns and hand burns," Priselac said.
Eggleston's daughter, who was inside the home, was also injured.
Priselac said, "The mother, who is pregnant, was Life Flighted to Hermann Memorial Hospital."
They are both in critical condition. Eggleston's two-year-old grandson is in fair condition.
The father was on scene with investigators as they tried to determine what caused the damage to the home and led to one death and injuries of his entire family. Investigators aren't saying yet if the fire may be weather related.
"Right now until we conclude and finalize the investigation, we'll make that determination," Priselac said.
Investigators believe the fire started in a back bedroom, but the cause hasn't been determined.
