According to the prosecutor, Paul Caneiro shot his brother on the lawn of the mansion, went inside and killed the rest of the family, and then set a fire in the basement early November 20.
Each murder charge carries a maximum sentence of life imprisonment.
Paul Caneiro was face a detention hearing Friday, but his lawyers asked for additional time to review new evidence, the Associated Press reported Thursday.
"From there we allege that the defendant intentionally set fire at his home at or about 5 a.m. for the objective of both destroying evidence of his crime in Colts Neck and to also create the illusion that the overall Caneiro family was somehow victimized or targeted", Gramiccioni said at a news conference.
Paul Caneiro, the brother of a New Jersey millionaire who was killed along with his family, has been charged with their murders. The prosecutor says that Paul Caneiro then shot and stabbed Jennifer Caneiro and then stabbed the children.
The emergency call for the Colts Neck mansion fire came in at 12:38 p.m. - more than seven hours after the Ocean Township fire - and more than 20 fire departments responded.
Paul Caneiro pleaded not guilty today to charges of murder in the deaths of his brother, Keith, and his entire family, and then setting fire to both his brother's home and his own to cover up the crimes.
In explaining the timeline as to why the Colts Neck fire, which was started in the basement of the sprawling home, was not reported until 12:45 p.m. - almost seven hours after the Ocean fire -Gramiccioni said that it smoldered for a while before it was exposed to oxygen and then began to grow and spread to become visible from outside.
Gramiccioni alleged that Paul Caneiro first shot and killed his younger brother and business partner Keith Caniero outside of Keith's mansion in Colts Neck on the early morning of November 20.
(Facebook/NBC News) Paul Caneiro, 51, was charged with setting fire to his home Tuesday (local time) in Ocean Township.
Paul Caneiro's attorneys, Robert Honecker and Mitchell Ansell, said in a statement Thursday their client maintained his innocence and that his family "means more to him than anything else in this world". Their bodies were left to burn, police said.
Caneiro remains in jail on a charge of aggravated arson and was served with the new charges on Thursday morning. He said the fire was started in two exterior locations at each end of the house.
"One body, a man, was found outside the home, and the other three were recovered inside the home", Monmouth County prosecutor Christopher Gramiccioni told Patch.com.
Paul Caneiro was charged last week with aggravated arson stemming from the fire at his house. "Have no reason to believe that's the case, think it was targeted".