The 13-month-old conjoined twins Jadon and Anias McDonald are still undergoing surgery in a New York City hospital to separate them as of Thursday night. Although separating them at the top of the head is a risky procedure, the medical team says it is going well.

According to the twin’s surgeons, the procedure could cause one of them to lose some cognitive function. However, their parents hope that both of them will be okay. Still, they are prepared to spend months or years in rehabilitation to help the boys meet their developmental milestones.

The twins from Braidwood, Illinois share 1.5 centimeters of brain tissue. Conjoined twins are rare occurrences, only occurring once in every 200,000 births.

The twin’s parents, Nicki and Christian McDonald, as well as their three-year-old sibling and other relatives, have moved to Bronx last February where the surgery is being performed.

“I could almost keep them like this now. They’re so perfect. They are normal little boys, they’re normal, they are perfect,” says Nicki. Nicki has been an inspiration to many because of her faith and dedication.

Nicki and Christian quit their jobs so their twins could get help from a specialist in New York. They are able to stay in New York, thanks to the generosity of family and friends back home.

Of the twin, Jadon has it worse. According to his mother, he has breathing issues, feeding issues, as well as some vision issues. He also has hearing issues, heart failure and seizures during his short life.

Twins conjoined at the cranium are extremely rare. Without separation, surviving beyond the age of two years is also extremely rare.

The McDonald family has set up a GoFundMe page to help them meet the cost of the surgery as well as the twin’s medical needs following the risky procedure.