Heitor and Arthur Rocha, who were joined at the hip and shared many internal organs including intestines and a bladder, underwent 15 hours of highly risky separation surgery Tuesday into Wednesday.
But Arthur died overnight Friday after going into cardiac arrest, Globo reported.
Surgeons at the children’s maternity hospital in the central city of Goiania said Heitor was on a respirator and suffering from fever following the surgery, which left both boys with just one leg.
The twins had already undergone 15 operations prior to last week’s separation surgery.
The boys’ father Delson said in a Facebook post that he was stricken with grief but thanked both children for “transforming our lives.”