The children were in stable condition at a Chicago hospital on Monday following the fire at 2260 Wayne Street.
"To have two young children alive after that exposure to intense heat is nothing short of a miracle," Hobart Fire Chief Brian Taylor told The Times of Northwest Indiana.
Taylor said that when he entered the smoke-filled home, he discovered one of the boys -- age 3 -- lying face down and unconscious on his bed.
"I snatched him up right away," Taylor said. "He had potentially another minute left."
The boy's brother -- age 2 -- was rescued from his crib by Lake Station Lt. Robert Saylor.
Taylor said after learning that the boys were doing well that it was a huge relief.
"It's probably the greatest news I could receive," he told the newspaper.
Neighbors identified the boys' mother who died in the fire as 29-year-old Jennifer Teel.
Firefighters found her body at the base of the couch in the living room near where the fire started.
The cause of the fire is currently under investigation.