Damien Bendall, 31, is now alleged to have raped and murdered 11-year-old Lacey Bennett, as well as killing her brother John Paul Bennett, 13, their mother Terri Harris, 35, and Lacey’s friend Connie Gent, 11.
The charges come after four bodies were discovered at a house in Chandos Crescent, Killamarsh, near Sheffield, South Yorkshire, on September 19.
Bendall was due before Nottingham Crown Court on Friday for a plea hearing, but the case was adjourned to January 4 at the Crown court in Derby.
The murder charges allege he killed all four on a day between Friday September 17 and Monday September 20.
An inquest opening at Chesterfield Coroner’s Court previously heard the four died as a result of a “violent attack”.
The coroner’s court also heard how a relative of Bendall had phoned police to say the defendant had suffered a self-inflicted stab wound.
In a statement, the CPS said: “The Crown Prosecution Service has authorised a further charge for Damien Bendall, 31, after reviewing a file of evidence from Derbyshire Police. He has now been charged with rape of a girl under 13.
“Mr Bendall was previously charged with four counts of murder in relation to an incident in Killamarsh, Derbyshire.
“The additional charge was today confirmed to the court at a hearing held at Nottingham Crown Court.
“All are reminded that criminal proceedings against the defendant are active and that he has the right to a fair trial.
“It is extremely important that there should be no reporting, commentary or sharing of information online which could in any way prejudice these proceedings.”