Twins Israel and Levi from Brazil underwent a 10 hour surgery to separate them.
The 14-month-old boys were joined at the hip and abdomen. They shared intestines, a bladder and genitalia, said pediatric surgeon Zacharias Calil, a specialist in separating conjoined twins.
"It was very difficult, very complicated but we managed (to separate them)," Calil said. The brothers "came through the surgery well."
Israel and Levi had four legs but their shared lower bodies made the surgery the second-most complicated for conjoined twins. Twins with shared skulls create the most complex separation surgeries.
They traveled to the central Brazilian city of Goiana for the surgery from Fortaleza, capital of the northeastern state of Ceara.
The surgical team of about 30 doctors, technicians and nurses separated "the intestines, the urinary part, the hip and we rebuilt two bladders," said Calil, the team leader.
Preparations for the complicated surgery began when the twins were born in December 2010 as their mother received advice from a specialist.
In November, the family traveled to Goiania to begin the final phase before the operation, which involved using eight expanders to stretch the children's skin.
Calil said the expanders "were instrumental in closing the abdomen."
Now the children begin a complicated recovery stage in which specialists closely monitor the functioning of their organs and the emergence of possible infections, which could occur beginning the fifth day after the surgery.
Calil estimated Israel and Levi's chances of recovery at 50 percent. The surgery was the eighth time Calil separated conjoined twins.
The surgery cost about $465,000, which was subsidized by the state government of Goias, the doctor said.