The Irish teenager imprisoned in Egypt for the past 15 months is afraid that he could be there for 15 years.
Ibrahim Halawa (18) is now in his second year in prison after being arrested during protests in Cairo in August 2013.
His sister Somaia Halawa told the Herald that he is due to face a trial on December 1, 2014, alongside 500 other defendants.
"He is losing hope," Somaia said.
"A friend of his with a similar case was sentenced to 15 years and that is not helping him. He said that it is making him feel worse."
Somaia said that he is no longer able to send his sisters letters and the only communication that they have with him now is through their mother who visits him every week.
The prison guards were previously reading the letters he sent and using that information against him.
"The letters were very important for him to speak to us and say what he wants but he cannot do that any more," Somaia said.
"Even if they allow him to send the letters, they read the letters first, so he has no privacy to talk about how he feels or to what he is going through."
Ibrahim was just 17 when he was arrested alongside his three older sisters in August 2013, after the ousting of Egypt's first democratically-elected president, Mohamed Morsi.
They were attending a wedding in the country at the time.
The Halawa siblings were seeking refuge in a Mosque when Egyptian police surrounded the building and arrested all the occupants.
Somaia (29), Fatima (23) and Omaima (21) were released from prison last November, returned to Ireland but they cannot go back to Egypt.
After a series of beatings, Ibrahim was moved to another prison but Somaia said that he is struggling there due to ill health.
"Last week he was not feeling well because it was very cold and that was affecting him," she said.
"Everyone in the prison is smoking 24 hours a day so his chest is rough and he has a very bad cough.
"It gets very cold there at night. There are no windows. Just holes in the wall and the air can come through," she added.
Despite the fact consular officials, including the Irish Ambassador to Egypt, have visited Ibrahim on more than 20 occasions, most recently on September 30, Somaia has called on the Government to do more to help her brother.
"I was in prison, so I know how it is. I know the situation," she said. "The more pressure they get [in Egypt] from someone they will begin to think 'this is going to make Egypt look worse'.
"Even if they don't ask for his immediate release they can ask for his evidence. If there is no evidence they will have to release him," she added.
A spokesperson for the Department of Foreign Affairs said that Minister Charlie Flanagan has requested a review, adding: "Minister Flanagan has asked that the charges against Ibrahim Halawa be reviewed, and that he be released and permitted to return home to Ireland."