Harriet Wran, 26, was arrested with a man, 35, at Liverpool late on Wednesday, before being charged with murder, attempted murder and aggravated break and enter.
Both were refused bail and are expected to appear at Liverpool Local Court today.
It follows the arrest of 29-year-old Lloyd Edward Haines from Telopea on Tuesday. He was also charged with murder, attempted murder and aggravated break and enter. He appeared at Parramatta court on Wednesday and was refused bail.
Emergency services were called to a unit block in Walker Street about 7.45pm on Sunday. Mr McNaulty was found with several stab wounds and died at the scene.
A second man, aged 42, also sustained stab wounds and was taken to St Vincent’s Hospital, where he remains in a stable condition.
Mr Wran, who was the state's Labor premier from 1976 to 1986, died on April 20 this year. Harriet and her brother, Hugo, were with their mother Jill at the public memorial for their father at Sydney Town Hall. The service was attended by former Prime Ministers Bob Hawke and Paul Keating, along with other Labor leaders and politicians.
According to her Facebook page, Harriet is currently studying modern history at the University of Sydney.
The Sydney Morning Herald reported a close friend of the family said Ms Wran had become involved with a bikie.