Dimin Wan was a devoted son showing his elderly Chinese parents around Victoria when he drove through a stop sign and into a truck.
His distraction cost 86-year-old Jiazhu Wan and Qian Shen, 85, their lives.
Wan was jailed in Victoria's County Court on Friday for a maximum of 18 months.
The 53-year-old said he took his eyes off the road for one-to-two seconds before May 2019 crash.
He'd been concerned for his father, who had groaned while sitting in the back seat.
But Judge Rosemary Carlin said this didn't explain why Wan, who until then had an "impeccable" driving record, failed to notice the intersection.
"Yours was more than a mere momentary lapse of attention," she said.
"It is really unfathomable how you could have missed so many warning signs as well as the intersection itself."
She acknowledged Wan had been a "devoted son" and didn't mean to harm or kill his parents.
"The consequences of your actions haunt you every single day," Judge Carlin said.
Wan was on the way back from showing his parents the popular Arthurs Seat lookout when he crashed.
It was only then he noticed the give way signs around the Mornington Peninsula intersection.
"There's a sign, there's a sign" he told one witness in surprise.
Wan was overwhelmed with guilt, and developed depression and post-traumatic stress disorder.
He could no longer work or drive.
His family forgave him and did not want him to suffer more than he already had.
Wan pleaded guilty to two counts of dangerous driving causing death.
Judge Carlin ordered he spent nine months behind bars before becoming eligible for parole.