A brother of Fishmongers' Hall killer Usman Khan has apologised in court to the families of those killed, saying: "We are truly, truly sad of the events that happened."
The sibling, who cannot be named for legal reasons, condemned his brother's actions, saying he was unaware of any plans to carry out the atrocity in which Khan fatally stabbed Cambridge graduates Jack Merritt, 25, and Saskia Jones, 23, at a prisoner education event in central London 18 months ago.
The witness also explained how, when news of the attack began to emerge, Khan's mother was concerned that her son had been harmed in the bloody rampage, not that he was responsible.
Giving evidence at the inquests into the deaths at City of London's Guildhall, Khan's older brother by seven years turned towards grieving relatives and said: "First all, sincere condolences to Jack and Saskia's family.
"We are truly, truly sad of the events that happened.
"Whoever's been affected physically or mentally, we are really sorry as a family - really, really sad.
"I just wanted to get that off my chest."
Khan's brother closed his evidence by adding: "We totally condemn his actions. Totally condemn."
He shook his head as he did so.
The witness said that despite both living in a three-bedroom house between 2005 and 2010, the brother did not pay attention to what Khan was doing with his life, assuming he was "chilling with his friends" and that he "kept everything to himself".
When Khan became involved in distributing extremist literature in 2008, and later admitted charges linked to a terrorist plot to bomb the London Stock Exchange, the news was "a total shock" to his family, the court heard.
The witness was shown pictures from local Stoke paper The Sentinel of Khan holding extremist leaflets and waving a jihadi flag in the street, as well as with extremist Anjem Choudary.
Nick Armstrong, for the family of Mr Merritt, told the witness that despite his claims that his brother kept everything to himself, he was "literally standing in the street waving a flag".
He also suggested that Khan had invented a story that he was expelled from school to come across as "a bad boy" and described Khan as "deeply disturbed".
Mr Armstrong said: "He (Khan) was a nasty, violent, self-regarding piece of work.
"All the signs were there, and you looked away, didn't you?
"You saw none of that."
The witness looked down and mumbled a brief, inaudible reply.
After his release from prison in December 2018, the witness said Khan would regularly visit the family home but would routinely dismiss any queries from them about his past.
The brother said: "He used to brush it off (and say) 'don't think about the past'.
"He said: 'I was young, I was silly, I got into stupid things'."
The inquests have previously heard how Khan was involved in a string of violent incidents and "extremist bullying" during his eight years in seven prisons for planning a terrorist training camp.
Jurors were also told Khan had been an "influential" inmate who associated with other high-profile terrorists including Fusilier Lee Rigby's killer.
He had engaged with prisoner education programme Learning Together while in jail, and he travelled to London from his home to attend a five-year celebration event at their request on November 29 2019.
The witness said he saw Khan the Sunday before the Fishmongers' Hall attack and said he had no idea he was plotting his attack, after evidence suggested Khan went out to buy gaffer tape used to strap knives to his hands an hour after the pair saw each other on November 20.
The witness said: "If I had seen anything, I would have relayed it."
Khan was pursued on to nearby London Bridge by three bystanders, armed with a fire extinguisher and a narwhal tusk in an attempt to disarm him, where he was shot by police.
The inquests continue.