Meni Jonathan was hospitalized last week in Abuja after a sudden illness, the Leadership, a Nigerian newspaper, reported. He died Tuesday, his older brother's 55th birthday.
Reuben Abati, the president's communications adviser, said the family is planning the funeral.
Meni Jonathan became ill last week in Bayelsa in southern Nigeria and was transferred to Abuja to get better medical care, the family said. The nature of his illness and cause of death have not been announced.