ITV News International Affairs Editor Rageh Omaar reports
A British family have described their devastation to ITV News after discovering a close relative is fighting with the Islamic State in Iraq.
In a video posted on social media, Hamzah Parvez - speaking with a London accent - claims to have left the UK to join Islamist militants.
Hamzah's family said they "feel betrayed" by his actions.
He had led them to believe he had gone to Germany until he contacted them earlier this week.
His family now want to warn others of the dangers of radicalisation.
The jihadist claims to have been fighting mostly in Iraq for between five to six months.
In the footage, Hamzah hails the "golden era of jihad", before saying: "What are we doing sitting in the UK?...It's not the land for us."
He urges people unwilling to fight for IS to "stay silent" and not to discourage others from travelling to Iraq and Syria.
He says there are "jobs for doctors, nurses, architects, builders even for street cleaners in the Islamic State".
"Are we content with eating Nando's every week? Come to the land of jihad and shout Allah," the jihadist said.
A family member said Hamzah is virtually unrecognisable from the person he previously knew.
"I don't recognise him, that's just the same body," he said.
"I don’t know he’s intentions, but his soul was wasted he was so nice… people like him, you never came across people like him…always smiling, always telling jokes, always making people happy."
Despite pleas from his family to return home, he refused, instead asking them to join him.
International Affairs Editor Rageh Omaar said: "Hamza's family supported him to go and study in Germany and they helped finance that.
"He went and failed to get in contact. He only called a few days ago to tell them where he was.
"They said they had raised the alarm once they were not able to hear from him in Germany.
"The Islamic State and other radical groups make a lot of videos which can't be verified, but we've been able to speak with the family.
"They say he has met other British fighters out there. He was not fighting so much at the moment, he was based in the Anbar province in Iraq.
"I've seen pictures which Hamza has taken which - having travelled to Anbar province many times over 12 years - looks like that kind of terrain.
"This is a very rare chance for people to see, in the raw, the immediate impact on the families. The Metropolitan Police recently urged families who had had contact who knew relatives who had taken the same path as Hamzah to contact them.
"When you see families going through that you can understand the absolute devastation and sense of loss that it throws them into."