Jacob Calero, 39, and Michelle De La Vega, 32, were taken into custody Wednesday as they arrived home on a flight to Oakland. They had left town Friday to celebrate the new year, authorities said.
The couple apparently told 9-year-old Joshua to look after his 5-year-brother, Jason, who is autistic. The children spent one night alone before police found them.
The parents said they couldn't find anyone to look after the boys,
Their grandmother, Libbey Holden, said she called police because she had suspected the couple left the children at home in San Ramon, about 35 miles east of San Francisco.
"I had big concerns," Holden told reporters. "These kids are helpless. (They), like any other kids, or any other human beings, deserve the love, time and affection of a parent."
The parents did leave their cell phone numbers, just in case the kids needed anything, says Blackstone.
"We made several attempts to contact the parents on both cell phone numbers we had available to us and that were provided to the children in case there was an emergency. Those calls went unanswered" until Tuesday, said San Ramon, Calif. police Sgt. Brian Kalinowski.
Holden told Blackstone that, when she heard of plans for the Vegas trip, she told the boys' new stepmother the children should go with them. But Holden quoted the stepmother as responding, "We are newlyweds, and we are working. We deserve a vacation."
Holden and her husband say they now want custody of the boys, Blackstone reports, but at a court hearing Thursday, she was ordered not to speak publicly about the case any longer.
The children's mother, Holden's daughter, died of cancer in 2003.
Joshua told The Associated Press his father and stepmother got each other puppies for Christmas, which they brought to De La Vega's mother to care for before leaving town.
"I thought they loved them more than us," Joshua said to the AP during an interview."