Emwazi was born in Kuwait before coming to Britain at the age of six. He attended school and the University of Westminster in the UK.
His family claimed to have lost contact with him in 2013 when he headed to Syria, telling them he was planning to help deliver aid. He re-emerged last year in Islamic State (Isis) videos showing the apparent murder of at least five Western hostages. It is not clear if both of his parents are currently in Kuwait.
"It's very shocking to see how he turned out: a mouthpiece for a terrorist organisation. His father is very distressed over what happened to his son. He's not well," said a family acquaintance, who only gave his first name, Tareq.
Emwazi's former head teacher said yesterday that the 26-year-old had been bullied at school but appeared a hard-working and aspirational young man who went to the university of his choice.
"Even now when I'm listening to the news and I hear his name I feel the skin on the back of my neck stand up because it is just so far from what I knew of him, and it is so shocking and horrendous the things that he has done," said Jo Shuter, the former head at Quintin Kynaston academy in northwest London.
Two other former pupils from the school have been killed fighting for extremist groups abroad. Choukri Ellekhlifi was killed in Syria in 2013, while Mohammed Sakr died fighting for al-Shabaab in Somalia. The Department for Education said that it would be carrying out a review of schools where children had gone to Syria to try to learn lessons for the future. Home Secretary Theresa May was yesterday summoned to the Commons after Labour demanded an inquiry into whether the decision to abandon the control orders regime had made it easier for a group of young extremists, including Emwazi, to travel abroad.
The control order regime was replaced in 2012 after a series of successful court challenges by terrorist suspects against restrictions on their movements, and relocation to other parts of the country.
Emwazi a 'model worker'
The unnamed Kuwaiti IT firm, which hired Mohammed Emwazi during a stint in the Gulf before he eventually fled London for Syria in 2013, described him as "the best employee we ever had".
"He was very good with people. Calm and decent. He came to our door and gave us his CV," the boss told the Guardian newspaper.
"How could someone as calm and quiet as him become like the man who we saw on the news? It's just not logical that he could be this guy." He said Emwazi left the firm when he returned to England abruptly in 2010.
The Telegraph reported that Emwazi changed his faith and became more radical after meeting a one-time confidant of Osama bin Laden known for recruiting Western-based Islamists to stage attacks on their own countries.
Emwazi met Mohsin al-Fadhli, a native of Kuwait who later led al-Qaeda's Khorasan network, in 2007, about the same time he also encountered Khalid al-Dossary, a Saudi national now serving life in a US prison for attempted bomb-making, Kuwaiti security sources have said.
So profound was the effect of their ideas on Emwazi that he renounced his Shia faith and converted to the Sunni creed adhered to by Isis.
As a member of al-Qaeda, al-Fadhli - who is thought to have been killed in a US strike in Syria last September - was once so close to bin Laden, the group's leader, that he is believed to have been one of a small select group to know about the 9/11 terror attacks on New York and Washington in advance.
In other developments:
US forces are targeting Emwazi. Asked whether the US was "going after" Emwazi specifically, Democratic Senator Dianne Feinstein said it was. "Oh, yes. He's a target. There should be no question about that," the former Senate Intelligence Committee chairwoman told CBS television's Face the Nation.
Isis and al-Qaeda jihadists are using pornographic images to hide secret messages sent to their followers on social networking websites, a new book claims. Messages have been found in "X-rated pornographic pictures which conceal documents and orders for the next target", according to Gordon Thomas in his new book on Mossad's cybercrime unit. Al-Qaeda has previously transmitted messages to followers through the online marketplace eBay, encrypting them in goods it offered for sale, according to the book, Gideon's Spies: The Secret History of the Mossad.
British ministers have ordered an inquiry into Emwazi's secondary school after it emerged two other former pupils went on to become terrorists. Two dead Islamist fighters were also taught at Quintin Kynaston Academy in north London. Choukri Ellekhlifi, 22, was killed fighting with terrorists in Syria in 2013 after joining up with an al-Qaeda group, while Mohammed Sakr, 27, died fighting for Al-Shabbab in Somalia.
Senior police officers revealed yesterday that about 60 British women and girls have travelled to Syria amid warnings of a campaign by Isis to target vulnerable teenagers to become brides for jihadist fighters. More than a third had been reported missing by their families with most aged 20 or under, said Helen Ball, the senior national co-ordinator for counter-terrorism.
New CCTV images emerged of three girls who travelled to Turkey 13 days ago. Footage released by a Turkish television station showed three girls, believed to be Shamima Begum and Amira Abase, both 15, and Kadiza Sultana, 16, walking into a bus station and remaining there for about 18 hours.
Iraq's state TV said last night that government forces backed by allied Shia and Sunni fighters have begun a large-scale military operation to recapture Saddam Hussein's hometown of Tikrit from Isis. Al-Iraqiya television said the forces were backed by artillery and Iraqi fighter jets.
- PA, AFP, Telegraph Group Ltd, AP, Independent