The blaze broke out just before noon on the 100 block of Sparks Street. It took about 45 minutes to get the fire under control but it was too late for the two boys under the age of 12.
The injured include four other children under 12 years old -- one of whom is an infant -- two adult males under 30 and an adult woman under 30. Their conditions ranged from stable to critical, according to fire officials.
Two families who were related to one another lived in the row home, said Fire Commissioner Lloyd Ayers.
Breaking news and the stories that matter to your neighborhood.
"You just have to pray for the rest of the family because some of them are in bad shape," the boys' after school counselor said.
The cause of the deadly blaze was under investigation but it appeared that there were many extension cords and space heaters being used in the home.
There was no battery in the only smoke detector in the house, Ayers said.
The house was gutted by the flames. Two adjacent homes were also damaged, according to authorities.
Fan, follow and download: Get the latest from NBCPhiladelphia.com anytime, anywhere. Follow us on Twitter, Facebook and NBC Philadelphia. Sign up for our breaking news newsletter. And, get breaking news delivered right to your mobile phone -- just text PHIBREAKING to 639710 to sign up. (Message and data rates may apply.)