Valhalla, N.Y. ? One year after a neurosurgeon separated them by cutting through a section of brain, Carl Aguirre says “Wow!” as he whizzes a toy truck off the tray of his high chair and his brother Clarence holds his nose to let his mother know his diaper is dirty.

After “starting their life over,” the formerly conjoined 3-year-old Filipino boys have been amazingly free of significant complications, doctors say. Clarence is about to take his first steps and therapists say Carl will soon follow.

“When they emerged from the OR as separate boys, it was almost as if that was their second birth,” said Dr. Robert Marion, the boys’ pediatrician. “Their motor skills are what you’d expect of a 1-year-old. They’re starting to walk. They’re playing appropriately in the way that a 1-year-old would. Their speech, also, is like that of a 1-year-old.”

Until last Aug. 4, when they underwent the fourth in a series of major operations at the Children’s Hospital at Montefiore Medical Center in the Bronx, Carl and Clarence had been unable to sit up, stand straight or see each other’s face. Joined at the top of their heads, they were limited to lying on their backs, which stunted their development and subjected them to chronic pneumonia caused by inhaling food.

“They were going to die,” Marion said. “And now seeing them with unlimited potential, it’s the most gratifying experience I’ve ever had in medicine.”

The boys and their mother, Arlene, came to New York in 2003, when Montefiore agreed to take the boys’ case for free – it has cost more than $3 million so far – and the Blythedale Children’s Hospital in Valhalla agreed to donate housing and therapy.

The Children’s Hospital team of neurosurgeon Dr. James Goodrich and plastic surgeon Dr. David Staffenberg separated the boys in a gradual “staged” approach, pushing apart their brains and dividing the blood vessels in four operations from October 2003 to August 2004. In between, the boys were given time to heal. It was a departure from the more common single marathon operation.

Formerly conjoined twins Carl, left, and Clarence Aguirre, spend time working with their physical therapists Mara Abrams, far left, and Barbara Milch at Blythedale Children's Hospital in Valhalla, N.Y. The 3-year-old boys are wearing custom-built plastic helmets so that the rebuilding of their skulls can be postponed and they can stay in therapy designed to get them walking and talking.

During the final operation, the surgeons found that the boys’ brains, which scans had indicated were abutting but separate, were actually shared and seamless at one point.

Dreading whatever complications he might cause, Goodrich studied and consulted and finally found a place to cut where veins seemed to go in opposite directions.

“I am not a religious person,” Goodrich said last week. “But I do think there was something guiding us along there.”

Marion said Carl suffered some seizures in the month after the separation, but Goodrich said his principal fears – neurological problems and liquid on the brain – did not develop.

During a reporter’s recent visit to Blythedale, Clarence walked proudly, holding onto a therapist with one hand and pushing his stroller with the other. He was so energetic that at one point he stepped out of his pants and staffers had to find him a belt.

Meanwhile, Carl stood, a bit unsteadily, to play a bead game on a table.

Later, the boys laughed as they tumbled down a padded slide together. Though their skulls have not yet been reconstructed – doctors don’t want to interrupt their therapy – and specially designed plastic helmets haven’t fit well, the doctors say the boys’ heads are protected well enough by their bandages even for horseplay.

Arlene Aguirre says she is encouraged when she hears Clarence say “yogurt” and call his brother by name. Carl says “walk” and “mama” and both boys use sign language to convey such phrases as “please more eat.”

Aguirre said she expects to move from Blythedale soon and set up a household with the boys, and hopes to eventually return to the Philippines.

“My friends and family, I want to share the boys with them,” she said. “It will be so exciting to go back there, holding one boy with each hand.”