text: Joe Robinson, 24, who lives in Leeds, was with his fiancÃ©e Mira Rojkan and her mother when they were arrested in the coastal town of Didim.
  He is thought to be under suspicion of sharing material on social media from his time in Syria with Kurdish militia.
  Lawyer Kaya Sertkaya said: "We do not know when he will be taken to court."
  Mr Robinson previously served in Afghanistan with the British Army, but in 2015 he travelled to Syria and spent time with Kurdish rebels the YPG who are fighting against so-called Islamic State (IS).
  He spoke openly about his experiences in newspaper reports at the time.
  The YPG is considered by Turkey to be an offshoot of the Kurdish militant group PKK that has waged an insurgency inside Turkey since 1984.
  But the YPG is not a proscribed group in the UK, and is considered a close ally of the US in the fight against IS.
  Speaking to the BBC, his father Andrew Robinson appealed for diplomatic help.
  He said: "When I heard that he'd been arrested on terrorist charges, I was devastated. I didn't realise what the situation was like in Turkey.
  "We're just hoping that somebody is going to come through and help us - the government, the Foreign Office. We're just hoping that somebody can get more information."
  Sharon Robinson, his mother, described his arrest as "the most ridiculous thing I have ever heard in my life".
  His lawyer said Mr Robinson was currently in jail in the west Turkey town of Aydin and his client was accused of "being a member of a terrorist organisation".
  "I was able to see him yesterday, he looked fine and in good spirits but we do not know when he will be taken to court," Mr Sertkaya said.
  "Because of the state of emergency, when arrests on terror charges are made it takes a long time for the prosecutors to write the indictment."
  He added: "Probably he will not be taken to court before three months or so."
  The Foreign and Commonwealth Office said in a statement that it was providing support to the family and remains in contact with the Turkish authorities.
  Turkish affairs analyst Guney Yildiz, from the European Council on Foreign Relations, said it was "not a surprise" that Mr Robinson may face legal action in Turkey for being seen to have had ties in the past with a group that Turkey regards as a security threat.
  "Turkey is more afraid of the propaganda aspect of a British national fighting with the Kurds against ISIS," he explained, "rather than that person being a real threat to public security in Turkey."
  Ms Rojkan, originally from Bulgaria and a student at the University of Leeds, was held in detention for six days before she was released under judicial control. Her mother was also released.
  "We are both innocent and we want justice," she said.
  Correction 17 August 2017: An earlier version of this story gave the wrong name for Joe Robinson's lawyer, Kaya Sertkaya.
target: An ex-British soldier held in Turkey on a terror charge while on holiday may be imprisoned for three months before the case reaches court, his lawyer said.