The next four months will give their brains time to recover since their separation surgery in October.
Dr Kenneth Salyer, craniofacial surgeon at Medical City, Dallas, said at a news conference on Monday that two-year-old Ahmad and Muhammad Ibrahim have made a remarkable recovery.
But doctors are not yet ready to start a series of surgical procedures to build new skulls.
"The word that we are getting from the neurosurgeons is that it is probably in these boys' best interests that we not reconstruct them too early because of irritability of the brain," Salyer said.
The boys are both active, with mobility in all of their limbs, and are learning to speak in English and Arabic. But it will take years to see if they can fully recover from the surgery that separated them from the crown of their skulls, Salyer said.
"We are very enthusiastic about the end result," Salyer said.
Salyer said Ahmad has had some regeneration of bone around his skull. He added that the brains of both boys will be largely exposed in the surgery to reconstruct their badly misshaped heads.
"We are very enthusiastic about the end result"
Dr Kenneth Salyer, surgeon
Medical City, Dallas
The process to rebuild their skulls will take years. Synthetic material, along with their own bone tissue stored in their bodies, will be used in the process.
The boys had a treat recently when they went to a holiday party for child patients at the hospital. They had their picture taken with several Dallas Cowboys cheerleaders.
The boys were separated in a 34-hour operation. They avoided for the most part post-operative complications such as infection, blood clots, or brain swelling - all of which could have proven fatal.
They were born in a town 800 km south of Cairo on 2 June 2001.