Abdu Rivera, 32, was arrested on Monday. He is charged with five counts of murder, arson and related offenses.
The fire erupted on November 18, 2003 at 3:30 a.m., in a home on the 100 block of Widener Street in the Olney section.
Police said at a news conference on Tuesday that one of the victims, 23-year-old John Santiago, was involved in a fight earlier that night with Rivera and a few other males outside a club at 2nd and Ontario.
Santiago, who was a boxer, got the best of his opponents.
"He was able to defeat two or three of them," said Capt. James Clark.
After the fight, however, Rivera and his friends allegedly went to Santiago's home, looking for revenge.
"Because of their pride being hurt they found out where he lived, came to the house, and set the house on fire," said Clark.
Also killed were Santiago's three-month-old daughter, Jacqueline, and the baby's mother, Clarissa Davila.
Santiago's mother, 41-year-old Francesca DeJesus, also died.
Santiago's 17-year-old brother, Alex, was seriously injured in the fire and died a few weeks later.
Three family members managed to escape the fire.
Fire officials determined the blaze was intentionally set after finding the remains of a plastic container in the living room that had remnants of a flammable liquid inside.
Police say the back door of the home was bolted and the victims couldn't get out.
During the initial investigation, police say witnesses refused to come forward and the original detective eventually retired.
There was no movement on the case until 2014, when two homicide detectives, John Verrechio and Tommy Gaul, reopened the investigation.
Those detectives were praised by Clark for their hard work, diligently working until an arrest warrant could be issued.
There was a $100,000 reward in this case and Clark said someone will be getting that reward.
More arrests are expected.