Destiny Ledwell and five others were inside the home in the 2400 block of Nebo Street when it caught fire Sunday morning.
Four people were able to escape unharmed and a fifth person was treated at a local hospital for smoke inhalation and released.
Fire investigators said foul play isn't suspected but haven't said what caused the blaze. Destiny Ledwell's brother said Monday that he believes it started because of an electrical problem in the home.
Chris Ledwell, 16, said he smelled smoke around 7:15 a.m. and tried to get everyone out of the house. His sister's door was locked, he said.
He said the family is heartbroken.
"Just keep us in your prayers," Chris Ledwell said. "We just need all the help we can get at this point, because we lost everything, including the love of our life."
The Durham chapter of the American Red Cross is providing financial and emotional support to the family and temporary housing.
A rising seventh-grader at Shepard Middle School, Destiny Ledwell dreamed of being a doctor, family members said.
"She was just a child, and that's what makes it more difficult," her grandfather, Bobby Ledwell, said. "She had not even begun to really live her life."
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