Abdullah Morsi, 24, died late on Wednesday as a result of heart attack at an Egyptian hospital, family sources told Anadolu Agency.
Morsi family lawyer Abdel Moneim Abdel Maqsoud said that the funeral was attended by his family.
The lawyer also said that the Egyptian authorities allowed his jailed brother Osama Morsi to attend the burial.
Egyptian authorities have not yet made any comment regarding the death or revealed autopsy results.
The family has ruled out crime as the cause of death.
Abdullah Morsi was an outspoken critic of the Egyptian government and had accused Egyptian President Abdel-Fattah al-Sisi of killing his father. He had been in and out of prison several times over what legal observers say were trumped up charges.
Mohammad Morsi, Egypt's first democratically elected president, died of a sudden heart attack in June while he was in court. He was ousted in a military coup in 2013.