"The dream of my life, to hold each of them separately, has come true. I thank God for this miracle and thank everyone who helped us in Egypt and in the United States," their mother, Sabah Abu el-Wafa, said after the family landed at Cairo's airport on Sunday.
The boys, born on 2 June 2001 in a small town in southern Egypt, were taken at age one to Dallas by the World Craniofacial Foundation, a Dallas-based non-profit group that helps children with deformities of the head and face.
More than 50 medical personnel, including several neurosurgeons and plastic surgeons, took part in the 34-hour separation operation in October 2003 at Children's Medical Centre in Dallas.
Doctors had warned that the surgery could result in the deaths of one or both of the boys. But the family decided it was worth the risk to give the children a chance at a normal life.
Since then, the boys have undergone extensive therapy and had surgery to reconstruct their skulls. They still must wear helmets for protection.
"I pray to God to enable me to provide them with all necessary welfare," said their father, Ibrahim Mohammed Ibrahim, after the family landed.
The boys learned English in the
US and hope to continue in Egypt
He said the twins had learned English while in the US and he hoped to continue their education in English.
Nasser Abdel Al, the twins' Egyptian doctor, said they will keep the helmets for several months to protect their heads.
They must undergo physical therapy before they go back to the United States 18 months from now for further checking.
Dr Kenneth Salyer, a surgeon who founded the World Craniofacial Foundation, said on Friday that the two boys were coming along fine and there were no additional operations planned.
But he added that he will check on them again in six months to a year to see whether it is time to remove the helmets.
Ahmed, who gets around with the help of a walker, still has one area on his skull that is soft, but it is gradually filling in, Dr Salyer said.
The US doctor said Mohammed's skull is healed and solid, but the helmet offers protection: "He wants to turn somersaults and his head isn't ready for somersaults."
Twins joined at the head occur only once in every two million live births.
Another set of such twins, the 29-year-old Iranian twins, Ladan and Laleh Bijani, died of blood loss during a 50-hour surgery to separate them in July 2003.