He was demanding, had to be waited on hand and foot and endlessly complained about how he should have been "president" and was "needy" of being treated as a more important person.
Domestic life with Lindt Cafe gunman Man Haron Monis was "all about him" and, in the end, "he destroyed my family", says the brother of Monis' lover Amirah Droudis.
Amirah is in custody awaiting trial for allegedly murdering Monis' first wife, Noleen Hayson Pal, in 2013.
Speaking exclusively with news.com.au, John Aspros said in the years following the time that Monis - known to the family as "Michael" - lived in the Droudis family home in Sydney's west, "everything has gone bad for us".
"He intimidated Mum and Amirah, I think he scared them, but Mum cared for Michael, did his washing, and cook for him. She was a good cook too," Mr Aspros said.
"He felt like he hadn't been given the respect he was due, the promotion to important positions. But in our home he was treated well, yeah even spoiled a bit.
"He was a bit like a son to Mum and so when he died [in the Sydney siege] she took it very hard."
When Monis, under the name of Michael Manteghi, began living in the Droudis family home, he didn't appear to have a job.
"He walked in here (with) nothing and acted like he was the boss, he wanted to prove he was the boss. Basically, he had an ego problem," Mr Aspros said.
"He used to drive around on his Harley with my sister. They got big boots, leather jackets and helmets and he acted like he was tough.
Mr Aspros said during discussions in the house after coverage of international news, Monis would "talk about ISIS".
"He approved of ISIS, yes, and I think he manipulated my sister in that way. Actually, I think he was mad."
Since the arrival of Monis in his family's life about six years ago, and his dramatic departure in a hail of gunfire when police ended the siege at 2am on December 16, 2014, Mr Aspros has seen his family disintegrate.
Immediately following the siege, police raided his family's home at Belmore, taking bags of evidence but laying no charges.
Mr Aspros' sister Amirah, who Monis married in the year before his death, was placed in prison in March last year.
Their mother, Soula Droudis, who at one point had put up $1000 to get bail for her son-in-law Monis after he was charged with sexual assault over his spiritual healing business, "was under a lot of stress following the siege".
"But he was very secretive, he'd never tell what he was up to."
Mr Aspros said he, his sister Amirah and their mother had watched the siege unfold on television in December 2014.
He said it had been "very upsetting" and that Amirah had been "astonished and horrified" to discover her husband was the siege taker.
"Knowing Michael, I think he just thought he could go in there, take over, and everyone would do what he told them to and he'd just walk out again," he said.
But in the time between the siege and her daughter's imprisonment, Soula Droudis began to fail health wise.
"Mum got lung cancer, basically because she smoked and drank too much whisky, but I think she was so much under stress," he said. "When Amirah went to prison, Mum never saw her again."
Soula Droudis died on December 7 last year from cancer, and John Aspros held a Greek Orthodox funeral for friends and family, which his sister was denied permission to attend.
When prison authorities denied Droudis leave to attend her mother's service, "that was hard for Amirah, she was very frustrated she couldn't go", Mr Aspros said.
"She's doing pretty well in jail, given the circumstances, but losing Mum was very, very difficult.
"She's managed to hold her own in there. She's made some friends, lost a bit of weight, and she reckons the prison officers are all right.
"But it's a lifeline for her seeing her daughter and family visiting."
Apart from his mother's death, Mr Aspros has seen his stepfather - Amirah's natural father, Tom Droudis - go into a nursing home following a stroke.
"He knows about the Lindt Cafe siege. He knows Amirah is in jail, but he can't communicate," Mr Aspros said.
Since his sister's arrest, Mr Aspros' niece, Amirah's teenage daughter Anastasia, has gone to live with an aunt.
Mr Aspros said he wanted to dispel one myth about his sister, that she had taken the name "Amirah" to replace her birth name Anastasia following her conversion to Islam.
"That's not true," he said. "The family called her Amirah before she met Michael."
He said that his sister would defend herself against the looming murder charge in the trial which is due to start in the NSW Supreme Court on August 15.