Firefighters received reports that another person who lived in the building was unaccounted for, but officials said no body was found.
The cause of the fire was under investigation.
The victims' names were not released by authorities, but Jesus Icelo, who said he was the dead man's brother, identified him as Arturo Icelo.
Neighbor Iola Tuft said the fire was so hot she could feel it across the street. "I could see the flames going from the side of the house into the next house," she said. "It was really bad."
John Cappiello, a spokesman at Bridgeport Hospital, said an adult had been treated and released for smoke inhalation. He said another adult and two boys had been admitted for treatment of smoke inhalation and were in fair condition yesterday afternoon.
The three injured were identified as Juan Garcia, Jesus Icelo, 12, and Arturo Icelo, 15, said Michael Giannotti, city spokesman.
A firefighter was hospitalized with a broken leg, fire officials said.
It was unclear whether the home had working smoke detectors. Mayor Bill Finch, who surveyed the scene later in the day, said the Fire Department hands out free smoke detectors, and he urged city residents to take advantage of the program.
"This was a horribly tragic event, especially during the holiday season," Finch said in a statement last night. "It's always difficult when there's a fatality but even more so when one of the victims is so young."
The American Red Cross was helping 20 people, about half of them children, who were left homeless, an agency official said.
Neighbor Edgar Mambreno said the people killed were hard-working immigrants from Mexico who used to live in his house, but moved a few years ago when their family grew. The father was a painter, he said.
"They were good people," he said.
