Joshua Malmgren, 31, of Lower Township, was arrested at the scene after the crash on Tuesday night.
During a court appearance on Thursday morning, Malmgren could be seen crying. The judge ordered him to be held at the Cape May County jail on $50,000 bail.
Malmgren's sister and other family members cried as they heard of the more severe charges.
"He's never been in trouble, said his sister, Jessica, through tears of her own. Prosecutors said they are seeking a higher bail and said they are in the process of upgrading the charges, possibly to first-degree aggravated manslaughter.
For now, Malmgren is charged with two counts of 2nd-degree death by vehicular homicide, driving while intoxicated, reckless driving, failure to maintain a lane of travel and consumption of alcoholic beverage by an operator of a motor vehicle.
He could now get up to 30 years in prison if convicted.
The hearing on the bail increase was scheduled for Monday.
After the hearing, the Malmgren's girlfriend and the mother of two of his four children came to his defense.
"I understand, I feel so bad for that family, I wish I could take it back, I really do. But Josh, he's a good guy, he's a great guy. He works hard, he works 60 to 70 hours a week, he takes care of his kids. He's a great guy, he just messed up," said Elizabeth Melli.
The accident happened around 9:20 p.m. on Bayshore Road near the Green Creek Fire House in Middle Township.
The Cape May County prosecutor's office said an SUV struck the teens as they were walking along the shoulder.
Two cousins, Ashley Dauber, 13, and Nioami Lazicki-Gaston, 15, were pronounced dead at the scene.
Nioami's 14-year-old sister, Farrahanne, was also walking with victims but was not hurt.
"She got out of the way but, by the time she screamed out up ahead, this monster was already on top of them," said Nioami and Farrahanne's father, Bill.
Nioami called her mom at 9:10 p.m. to tell her they were on their way home. Then Farrahanne called eight minutes later to say there had been an accident.
"And then my other daughter called me at 9:18 to say they both got hit by a car," said their mother, Christina Lazicki-Gaston.
"That was the worst call a parent can ever get is that their children are lying dead."
Nioami and Farrahanne are from the area. Ashley had been visiting from Northeast Philadelphia.
The girls' parents say the driver robbed two young girls of their dreams.
"She just got into tech full-time. We were so proud of her. That was her main goal that she wanted to achieve was to get into tech. At least she had that before she left us," Bill Gaston said.