Shelly Wu, six, and Lily Wu, seven, were hit by Michael Junior in Handsworth, Birmingham, last June.
Junior, 35, had admitted two charges of causing death by dangerous driving and three charges of causing serious injury by dangerous driving.
The sisters were hit by his car while holding hands as they crossed the road on their way to Chinese classes.
Judge Murray Creed told Junior he had ended two young children's lives and injured two other children along with the girls' mother, Zhulan.
Mrs Wu had been left with "significant psychological trauma", the judge told him. The court heard she had to be sectioned earlier this year.
The other two children have since recovered.
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The court heard Junior accelerated to get around a bus just before a blind left-hand bend, leaving him no time to react as the family crossed in front of him.
He also ignored road signs warning of elderly pedestrians crossing, a sign reading "Slow" and chevron markings indicating a crossing ahead.
Prosecuting, Gareth Walters told Birmingham Crown Court Junior's speed was an estimated 47mph (75kmh) in a 30mph (48.3kmh) zone when he struck the family on Grove Lane.
Two of the four children survived but Lily and Shelly suffered fatal head injuries.
Judge Creed said Junior hit the pedestrians as they reached a central reservation.
"Mrs Wu [and the other children] hit the front and were thrown to the floor. But unhappily, the two smaller children were carried a short distance along the bonnet before being left to lie in the road, both fatally injured," he said.
Outside court, family friend Alex Yip read a statement on behalf of the family, saying: "Four years is not long enough - for us this is a life sentence."
He added: "We have had ripped from us two beautiful daughters, two sisters to our two eldest, two granddaughters, two lives taken from us all, from each and every day for the rest of our lives.
"We have lost the wife and mother we once had, the heart of the family, strong, independent, who we depended on, and who will never be that way again."
In mitigation, Timothy Harrington said Junior, of Copthall Road, Handsworth, wished to apologise to the Wu family but asked the judge to regard the incident as a "one-off", a single moment of bad driving.
Junior was also disqualified from driving for five years.
The sisters both attended Wilkes Green Primary School in Handsworth. The school said it had been raising money to create a peace garden in their memory.

North Wales Fire and Rescue Service responded to reports of a fire and smoke at an aluminium works at London Road, Holyhead, at 03:29 BST.
The A55 was closed for a short time between J1 A5 Victoria Road and London Road and J3 A5 (Valley) due to concerns about a risk of further explosions, said North Wales Police.
One fire crew remains at the scene.
Multiple agencies attended the site and, after checks, it was declared safe and roads were reopened, a police spokesman said.
A driver who knocked down and killed two sisters on a pedestrian crossing has been jailed for four years.
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Fire crews have been called to several reports of an explosion at Anglesey.