CHICAGO (CBS)– Scared to show their faces or reveal their names, the adult-twin daughters of Clarisa Figueroa describe the horror after learning, that their mother and half sister, Desiree, allegedly murdered 19-year-old Marlen Ochoa, took her baby, and tried to pass it off as their brother.

“They are monsters,” one sister said. “It’s just too much already, it’s just too much.”

The twin sisters said they are living a nightmare. They have received death threats and their children have been harassed. Because of this, they requested to hide their identity.

The twin’s mother, and her daughter, Desiree, 24, have been charged with one count each of first-degree murder and aggravated battery of a child. The elder Figueroa’s boyfriend, 40-year-old Piotr Bobak, has been charged with concealment of a homicide.

“My mom goes ‘Do you want to see your baby brother?'” one of the twins said.

That was April 24, the day after they say their mother Clarisa called to say she had a baby. The twins said they hadn’t seen their mom in nearly a year, but they did keep in contact over the phone.

The sister said her mom stayed in the hospital for three days, accompanied by her boyfriend Peter Bobak, who they confirm is seen in pictures with the baby.

One sister said she visited her mom, two days later on April 26.

“I seen the baby, and I touch the baby, and I didn’t think of anything about it wasn’t my brother because my mom said it was my brother,” one sister said.

Both women said they grew up in an unstable home and were neglected by their mother.

“I was a teen mom at the age of 16, and lived on my own since then,” one of the sisters said.

Both sisters admit they had doubts.

“They should have checked my mom. They should have made sure that the baby was hers. If they knew her tubes were tied, why didn’t you double check? Why didn’t you check that that was her baby,” a sister said.

The twins say they will not be able to forgive their mother and sister for killing Ochoa, cutting her unborn baby from her womb, and passing the baby off as Clarisa’s.

“I want to tell Marlen’s family that I am so sorry for what they are going through,” a sister said.

One of the twin sisters said she won’t attend her mother’s and sister’s court hearings; and if they are convicted, she will not visit them in prison.