Shenae Lyall, 16, and her brother, Troy Lyall, 20, died in a car rollover at Bute a year ago.
Two other passengers were injured.
The driver, Adrian O'Daniel, 22, was charged with two counts of causing death by dangerous driving and two of causing harm by dangerous driving but pleaded guilty in Adelaide Magistrates Court to downgraded charges of driving without due care.
The court previously was told O'Daniel was drunk at the wheel.
It heard he wanted to be part of a restorative justice process with the family of the victims.