The children died in a fire while their mothers were outside the home in the back parking lot.
Fairfield investigators say they have enough evidence to support manslaughter and child endangerment charges against both women. Shetarra James, 24, and Latisha James are sisters. The children were all cousins.
The victims, three girls and one boy, have been identified as Robert Christopher Charles, Jr., 4, Nevaeh Nunn, 2, Natalie Rogers, 2, and Keviana Morgan, 1.
At least one candle burning on a television set in a front living room was cited as the probable cause of the fire. PG&E confirmed power had been disconnected to the apartment for failure to make payments.
According to investigators, as many as three candles were burning in the room where the children were left alone, and there were combustible materials nearby.
Shetera James, who lost three children in the fire, told reporters that she did everything she could to get them out and wishes she could have done more.
"All three of my children are gone," James said. "I miss my babies," she said the day after the fire.
There have been no arrests in the case. That decision would come only if the prosecutor follows the investigators recommendations.