The family of a young British boy thought to feature in the latest Islamic State (IS) propaganda material have said the youngster is merely being used as "a shield" by the terrorists.
Henry Dare said he believes his grandson Isa was the unidentified child involved in the footage.
Police are working to determine whether the boy - thought to be aged under five - is Isa, one of the sons of Grace "Khadijah" Dare, a Muslim-convert extremist from Lewisham in south-east London.
Mr Dare told Channel 4 News: "He's (used) for propaganda. He doesn't know anything. They (IS) are just using him as a shield.
"She (Khadijah) should come back and face the music because she has left herself down. All of us, she's let us down."
The majority of the footage, which has yet to be independently verified, features a masked man who insults Prime Minister David Cameron, labelling him "an imbecile" for launching air strikes in Syria, before killing a prisoner. Four other men then kill one prisoner each.
He speaks in a British accent and appears to mimic the style of the British man known as Jihadi John - real name Mohammed Emwazi - who was killed in a US drone strike in Syria in November.
The boy makes a fleeting appearance in a desert landscape at the end of the 10-minute video.
Wearing camouflage clothing and black headband, he speaks in what sounds like a British accent and says: "We are going to go kill the kaffir (non-believers) over there."
Grace Dare was brought up as a Christian but converted to Islam and started using the first name Khadijah, her family said. She travelled to Syria in 2012 and married Swedish Islamic fighter Abu Bakr, who is believed to have been killed since.
Dare, who according to the Daily Telegraph has a younger son as well as Isa, had previously used social media to say she wanted to be the first British woman to kill a British or American ISIS hostage. Last year she was said to have posted a picture on Twitter of Isa with an AK-47 rifle.
A spokeswoman for Lewisham Council said: "We are unable to confirm the identity of the boy in the video. The council is liaising with the police and we are deeply concerned about any suggestion of a link between these abhorrent acts and our community."
It is not the first time children have been used in the group's graphic videos.
In one infamous image, a child was pictured holding a severed head, while another photograph that circulated online showed a young child being encouraged to kick a severed head.
More than 30 UK children had been made the subject of family court orders over radicalisation fears, Scotland Yard said in August. At that time, judges had considered cases involving 12 different families.
Assistant Commissioner Mark Rowley, the country's most senior terrorism officer, said in some instances the children were "almost babes in arms", with ages ranging from two or three up to 16 or 17.