The Sumer brothers are not so much close as a single organism. Ask one a question and two others answer on his behalf. Jokes are told in relays that end in harmonised guffaws.
''The strength is in our family,'' says Mustafa, the expansive eldest child. Sitting down from him in a dining room in Kings Langley are shy Ali, jocular Mehmet and taciturn Ertan.
Missing is Behic, the middle child the others call their ''buffer''. Ten years ago, Behic stopped off from a visit to London to join two of his brothers on a Bali holiday.
The last thing Ali can remember about Paddy's Bar is a bartender shaking a cocktail mixer.
''A fireball hit me,'' he said. He lay prone as a second bigger blast tore through the bar from a van parked outside.
The Turkish-Cypriot brothers identify with a secular brand of Muslim and remain confounded by the idea of someone invoking Islam to justify acts of terrorism. ''It's against Islam to kill,'' Ertan says. ''They are not basing it in teachings.''
But the brothers, who studied engineering together at university, are circumspect about what motivated the attack.
''The thing is the degree of their knowledge - they don't question,'' Mustafa says.
''Ignorant people are very dangerous things,'' Ali says. ''You can move them to do dangerous things and kill beautiful people.''
Ali came to in darkness, his skull perforated by the leg of a bar stool. As he brought himself to his feet he pushed his hands into a pool of molten plastic but felt nothing, his nerves and half his skin were burnt.
He walked to hospital, was flown to Adelaide and went into a coma. Ertan was also injured, in better condition than Ali but still would spend a month in hospital recovering from his burns.
Behic, however, was missing.
Against all advice, Mustafa flew to Kuta.
''I had to go find my brother,'' he said. ''Maybe he lost his mind in the bombing''.
Mustafa spent three weeks searching morgues and hospitals. Bearing photos of his brother, he followed up on every false sighting.
When they called to say Behic was discovered among the dead in Darwin he recalls the total absence of feeling.
In Adelaide, Mehmet took the news at Ali's bedside.
''I pray: 'God, I lost one, I don't want to lose him too; help me to stand up, to keep him, to bring him home,''' he says.
After two months, Ali opened his eyes and squeezed his brother's finger. ''I said, 'Thank God,''' Mehmet said.
By then, Behic's funeral had been held a month earlier at Auburn mosque.
Mustafa says the execution of his brother's murderers gave him no succour. ''These people are ex-Afghan veterans,'' Mustafa says of the terrorists. ''They became crazy like the people in the Vietnam War.''
For the insistently rational man, his ability to consider the motivations of the men who murdered his younger brother might be Behic's lasting influence.
Behic was, his brothers concede, the sharpest mind in a family of scholars. But in every situation his first recourse was an even greater sense of empathy.
His generosity made Behic a buffer not just between brothers but left and right, Greeks and Turks.
''He loved everyone,'' Mustafa said. ''He could see where everyone was coming from.
''He discovered logic is not what everyone uses: he taught me the logic of [being] logicless.''
Those memories are consoling, Mehmet says, but will not fill an empty chair.
''When we lost him, we are not the original Sumer brothers.''