In a nearly five minutes video, Paul Cantlie made the heartbreaking appeal sitting in a hospital bed. His voice was raucous as reports said he just underwent a throat surgery, Xinhua reported.
"As a family we experienced great relief seeing and hearing John and knowing that he is alive. This was followed by the feeling of despair and helplessness," said Cantlie.
John Cantlie appeared in a series of short films, which was recently issued by the IS. So far, there are three videos. It was the first time in almost two years that his family saw him since he had been held as a prisoner by the IS in 2012.
Holding the paper with the words he said, there's a tremble in Cantlie's hands and he spoke very slowly and with difficultly.
He said John had been working as an independent photo journalist, seeking out the true story of the suffering of the Syrian people and ensuring the world was made aware of their plight.
"John felt a strong need to help in the best way that he could: as an impartial and respected journalist he knew that he could make a difference by acting as a platform for the world to listen to and take notice, using his journalistic skills for the good of the people; as a friend and as a civilian," the father said.
"Speaking entirely for myself, this is not how I had imagined I would be passing my 81st year. I want John to know how very proud I am of him. I can think of no greater joy than seeing my dear son released and allowed to return home to us," he continued.
He said his family were trying to communicate with the IS, but they did not respond.
"To those holding John: please know that he is a good man, he sought only to help the Syrian people and I ask you from all that is sacred, to help us and allow him to return home safely to those he loves and who love him," he said.
John, a 43-year-old British journalist, used to work for the Sunday Times, the Sun and the Sunday Telegraph. He was captured by the IS after arriving in Syria in November 2012. The first time he was kidnapped was in July 2012.
His first video was released Sep 18, saying he would show some facts and truth in a series of programmes. In the second video, John Cantlie said that the Western countries underestimated the growth of IS, while in the third one, he criticized US President Barack Obama's tactics of using airstrikes and proxy Kurdish and Iraqi ground forces against IS.