They expressed disbelief that the 18-year-old, who detonated his bomb on the No 30 bus in Tavistock Square killing 14 on July 7, could have carried out the atrocity .
The teenager, from Colenso Mount, Holbeck, Leeds, was described as a "loving and normal young man who gave us no concern and we are having difficulty in taking this in."
The family's statement said: "Our thoughts are with all the bereaved families and we have to live ourselves with the loss of our son in these difficult circumstances.
"We had no knowledge of his activities and had we done we would have done everything in our power to stop him. We urge anyone with information about these events, or leading up to them, to co-operate fully with the authorities."
And the family of another member of the West Yorkshire-based bombing team – Mohammed Sidique Khan – claimed that they had been wrongly "criminalised and vilified".
According to Sir Iqbal Sacranie of the Muslim Council of Britain, who met Khan's mother-in-law Farida Patel, 65, a retired teacher, his family feel "utterly vilified".
"The son-in-law might be a criminal but they feel the family has been criminalised. Mrs Patel is afraid to go home. It's an area where the British National Party exists in big numbers."
"They also have to face the loss and what has happened," he said.
Khan, 30, of Dewsbury, who worked as a supply special needs teaching assistant at a Leeds primary school, is believed to have caused the Edgware Road tube blast which left seven dead.
The revelation that another of the suicide squad was 19-year-old Lindsay Jamal, a carpet fitter who came from Huddersfield and Beeston,Leeds, before recently moving to Aylesbury,Bucks, brought a reaction of denial and defiance from his widow Muslim convert Samantha Lewthwaite.
The 22-year-old mother said: "Hw wasn't the sort of person who'd do this. I won't believe it until I see proof."
The distraught widow of the bomber who is believed responsible for 26 deaths by bombing the Piccadilly Line between Kings' Cross a Russell Square, claimed he would never having willing abandoned her to raise their children alone.
"He was lovely - and we were just perfect together," she said.
"I had everything. But if this is true, then now I have nothing. But I won't believe it until they show me the proof. I'm not going to accept it until they have his DNA."
The former prom queen's father, Alan Lewthwaite,49, her mother Elizabeth and sister Sabrina have refused to be drawn on the allegations against Lindsay who met Samantha three years ago through their Muslim faith while attending a college in Luton.
Today it emerged that he was on a terror watch list but intelligence allegedly lost him.
The family of another of the bombing Leeds Metropolitan University sports science student Shehzad Tanweer,22,from Colwyn Road, Beeston,Leeds, who caused the Aldgate tube blast have remained tight lipped.
It is known that that Tanweer visited a school in Pakistan to further his Muslim studies.
Tanweer and Hussain met when they both studied at the Thomas Danby College on Roundhay Road, Leeds. Tanweer left in 2000 to transfer to the Metropolitan University and Hussain left in 2005 after completing an AVCE course in Business.
Today Scotland Yard anti-terrorist officers arrived in Cairo to interview their main suspect - Leeds University trained chemist Dr Magdy Elnashar who was arrested there yesterday.
Elnashar rented a flat in Alexandra Grove, Burley,Leeds, which is believed to have been the bomb making factory. He lived around the corner in St John's Terrace. He has denied any involvement in the outrages.
?Pakistan today detained two men in connection to the bombings.
bruce.a.smith@ypn.co.uk