A grandfather - who joined Islamic State in Syria with 11 other family members of his family - is being held against his will after being "tricked" into going, his son has told ITV News.
Muhammed Abdul Mannan, 75, his wife and 10 other members of their family, from Luton, have not been seen since leaving for a trip to Bangladesh in May.
A picture apparently showing Mannan in Syria emerged on social media last week, and a statement released by IS claimed the family were "safer than ever" now they had joined the terror group.
But speaking exclusively to ITV News, Shalim Hussain said his father was forced into a van and taken to Syria against his will.
Hussain said his father had been crying down the phone from Syria.
"My Dad is confused, sad, crying every day - [he's] not in peace," he told UK Editor Rohit Kachroo.
He claimed the family were in Istanbul when a group of men came to their hotel room to check their passports before taking them downstairs one by one.
When just the grandfather and his wife were left, they were told to leave their children and grandchildren behind and to return to Britain, Hussain said.
But when they refused to leave, Hussain claimed the men bundled the pair into two waiting cars.
Speaking about the image released of his father in Syria holding up a finger - a symbol associated with IS fighters - Shalim said it was not a show of support for the terror group, claiming it was just "pure propaganda" from IS.
A group photo of the family including those missing.
He insisted that there was no sign that any of his siblings had become radicalised or planned to flee to Syria.
Asked whether there were any clues as to the family's intentions, he said: "Not really, nothing unusual. If I did I would have stopped it. Police couldn't find anything radical. No proof, nothing suspicious.
"If it was something not normal or suspicious then it would have gone through my head but there was nothing. No signs. If there was a sign I would have picked up on it."
Hussain made an emotional appeal for his family to return home, saying his heart had "been empty" since their departure.
A spokesman for the Foreign and Commonwealth Office said they were working closely with both Bedfordshire Police and the Turkish authorities.
The UK has advised for some time against all travel to Syria. As all UK consular services there are suspended, it is extremely difficult to confirm the status and whereabouts of British Nationals in Syria.
Anyone who does travel to these areas, for whatever reason, is putting themselves in considerable danger.