Tayla Alexander, 17, died at the scene, while her sister Sunmara, 16, died two weeks later in hospital with critical injuries after the car they were in crashed on Summit Rd in the Port Hills at 11pm on November 27.
The 19-year-old driver has now been charged with two counts of dangerous driving causing death.
He's also been charged with dangerous driving causing injury and driving without the appropriate licence.
He will appear in Christchurch District Court on May 28.
Superintendent Lane Todd, Canterbury metro area commander said: "This was a devastating event and a tragic reminder to all drivers of the need to drive safely and to the conditions.
"Our thoughts remain with the family and friends of Tayla and Sunmara as they continue to grieve the loss of their loved ones."
Sunmara suffered extensive burns and died two weeks later. The battle to save her had meant multiple amputations due to infections.
Their father Jason Alexander's last words to his only children were: "I love you and be good."
The Covid-19 lockdown served only to amplify his grief. That has been compounded by delays in the justice system.
"I missed the girls so much I wanted to join them," he says.
"I didn't want him to go to jail for a silly mistake. He is young and is already going to have a lot to deal with for the rest of his life.
"Anger won't bring them back. The boy said he was going to Sunmara's funeral - but he was a no-show.
"I don't hate him but I understand why he hasn't made contact. I think he is really scared."
