Television actress Jessica Falkholt lost her parents on Boxing Day after Craig Anthony Whitall, 50, slammed into her family’s car.
Her sister Annabelle, 21, was critically injured at the time, with reports just in that she has now passed away.
“Annabelle passed away this morning, we knew what was happening so family were with her,” a relative told The Daily Mail.
“Her and Jessica had such a strong sister bond. They are seriously close sisters I feel Jessica would have known her sister passed.”
Jessica remains in St George hospital, where she has just undergone surgery.
Tributes have begun flowing in for Annabelle, a childcare worker that many referred to as “kind”.
“Annabelle worked at a centre in Lilyfield and some of her work colleagues came in here to see her yesterday,” a family member told The Daily Mail.
“She worked with young babies and she was very nurturing. She was very caring and she just loved children... she is such a kind girl.”
On Wednesday, NSW Chief Inspector Phil Brooks warned that the 2017 Christmas and New Year period was particularly tragic on the road this year, with 11 fatalities occurring after vehicles veered off the road.
"Out of these 21 deaths, 11 road users have been involved in matters where their vehicles have simply left the road and crashed into a telegraph pole or a tree,” he said in a press conference.
“There are more cars on our roads and sadly, personal responsibility is lacking many road users. The impact of road trauma is significant.
"Out of 433,000 random breath tests, 739 drivers are facing the courts in the New Year for a range of drink-driving charges putting themselves, their passengers and other road users at great risk right throughout the NSW road network."
He added that the state's road death toll was at 873 fatalities this year, up 12 from the same time last year.