The youngest son of the late Egyptian president Mohamed Morsi died of a heart attack in a hospital in Giza, south of the capital Cairo.
Abdullah Morsi, who was in his mid-twenties, had emerged as a spokesman for the family after his father died in an Egyptian jail on 17 June.
The younger Morsi, who died on Wednesday, had accused security officials of being behind his father’s death.
Days after his father died, Abdullah identified several figures, including current Interior Minister Mahmoud Tawfiq, his predecessor Majdi Abdel Ghaffar as well as Mohamed Shereen Fahmy, the judge who oversaw the ex-president’s trial, as “accomplices” in the “assassination of the martyr, President Morsi”.
Morsi, a member of the Muslim Brotherhood, was elected in Egypt’s first-ever presidential election in 2012, after a popular uprising overthrew longtime leader Hosni Mubarak.