Neighbors reported the fire started in the back of the two-story home.
The fire started just before 7 a.m. Wednesday morning in the 1200-block of Field Court in Naperville.
Investigators are still investigating the cause of the fire, but say a natural gas line was feeding the fire and that is what made it nearly impossible to reach the husband and wife trapped in an upstairs bedroom.
"It's always sad when we have a fatal fire, but especially around the holidays, it's always more difficult for everyone involved," said Dep. Chief Rick Sander, Naperville Fire Dept.
It was a fast moving fire. First reported just before Naperville firefighters were on the scene at 1212 Field Court within minutes, but they say, it was likely already too late for the husband and wife, both in their 50's, who died as a result.
"Those victims ended up on that bottom floor which was right next to a natural gas feed that did make it nearly impossible to make entry and recover the bodies initially," said Chief Mark Puknaitis, Naperville Fire Dept.
All told, there were five people inside the home at the time. An elderly man in his 80s and his daughter were in the process of self-evacuating when first responders arrived. A 21-year-old man was rescued unconscious from the second floor moments before it collapsed.
"They were all related except for one, the 21-year-old who was rescued. He was a caregiver," said Puknaitis.
Friends who stopped by the scene earlier said both husband and wife were disabled. She was blind and he was battling an aggressive brain cancer.
"He was absolutely committed to, I will live on and I will go through my chemo and radiation, he came out and he regularly ran, he was determined to keep himself motivated," said Leon Thomsen, victims' friend.
Thomsen said he just had come from the hospital visiting the survivors. The man in his 80s and his daughter are expected to make a full recovery. The 21-year-old caregiver remains in critical condition at Loyola Medical Center.
When firefighters arrived at the scene at 6:53 a.m., the house was engulfed in flames, fire officials said. They were able to go into the house to get some people out.
"Shortly after (a resident) was rescued from the second floor, firefighters were pulled from the building for fear of collapse," Thurow said. A news release said firefighters discontinued rescue efforts from the building 10 minutes after they arrived.
The house is in the Field Court in Naperville, which is located east of River Road between Jefferson and Aurora avenues.
The fire appeared under control by about 8:15 a.m., although responders were seen carrying what appeared to be breathing apparatus into and away from the house during the hour that followed.
Backup was provided by Bolingbrook, Downers Grove and Westmont fire departments, among others.
The Sun-Times Media Wire contributed to this report.
