An Australian couple was charged Thursday with murder and torture in the deaths of their 18-month-old twins, whose decomposing bodies were found by their older sister this week.

The mother, 30, and father, 28, had initially been charged with neglect after the woman told police the twins had starved to death, but the prosecutor upgraded the charges during their court appearance. Because Australian courts don't identify minors, the parents' names were withheld to protect the children's identities.

The murder and torture charges carry potential life sentences.

Australians have been horrified by the deaths of the two children, who had been dead at least a week before police were called to the middle-class suburban home. They weighed only as much as newborn babies: 9 pounds and 8 pounds.

The mother told the court she found the boy and girl dead last week, on Sunday or Monday, but did nothing about it, prosecutor Michelle Clark told the Brisbane Magistrates Court Tuesday.

Clark said the mother told police, "I don't think I fed them enough."

The father's lawyer, Michael Cridland, told the court that his client had not been responsible for caring for the twins and had not seen them since Christmas.

The Department of Child Safety was unaware of the twins, and neighbors said they did not know the family had young toddlers.

The twins were reported dead late Monday after an 11-year-old sibling found them in a bedroom of the family home.

The couple's surviving children — ages 3, 4, 5 and 11 — are being cared for by their grandmother. She told reporters Wednesday that the children were "very traumatized, but we are doing the best we can for them — just to know they are wanted and loved."