The Committee to Protect Journalism has called on the Egyptian authorities to immediately release the brother of the editor-in-chief of local news website Darb.
Kamal El-Balshy was arrested on his way home from the gym in downtown Cairo on 20 September.
El-Bashy, who is a travel agent, was charged with illegal assembly, membership of a banned group, spreading false news and misusing social media. He was detained for 15 days pending trial.
The day after his arrest El-Bashy was taken to Kasr El-Nil Police Station, where his family visited him, then taken to the Central Security Forces' training camp in Cairo.
Between 22 September and 1 October his family were not able to communicate with him.
"Egypt must release Kamal El-Balshy immediately and stop their harassment of Darb and its editor, Khaled El-Balshy. Journalists should be allowed to work freely, without fear that they or their relatives will be jailed," Ignacio Miguel Delgado, CPJ's MENA representative, said.
"Targeting a journalist's family is completely unacceptable."
Rights groups have said that his arrest was ordered in retaliation for his brother's job as a journalist. Khaled El-Bashy has been outspoken about the inhuman prison conditions detained journalists are kept in.
Political prisoners in Egypt are locked up in overcrowded cells with not enough food to eat. They are systematically tortured and denied urgent medical attention.
Khaled recently denounced the arrest of one of his journalists – on 9 September security forces arrested Islam Al-Kalhy, a Darb reporter, after he covered the protests outside Munib Police Station in Giza following the death of Islam the Australian.
Egypt has a long history of carrying out punitive measures against the families of Egyptians who criticise the regime, particularly if they live abroad and cannot be reached.
At the beginning of September Amr Ali Abu Khalil died of a heart attack in Scorpion Prison after his repeated requests for urgent medical care were ignored.
Abu Khalil was forcibly disappeared at the beginning of October 2019 after his brother, an Egyptian journalist and TV anchor for El-Sharq, released a report on corruption within defence minister turned President Abdel Fattah Al-Sisi's family.
In June, security forces raided the homes of former political prisoner Mohamed Soltan's family, arresting five of his male cousins, after Soltan filed a lawsuit against the country's former prime minister for torture from the US.