It is only thanks to his sister's testimony, however, that Wim finally went on trial in April for six gangland killings - including that of his and Astrid's childhood friend and brother-in-law, Cor van Hout.
The family saga of murder, revenge and betrayal has gripped the country: outside Amsterdam's main court, queues form each day at three in the morning to get a seat in the public gallery.
Wim has made plain from his prison cell that his associates on the outside are just waiting for a chance to carry out the death sentence he has declared on his little sister.
As a result, Astrid lives under police protection, moving from safe house to safe house, unable to work, meet friends or show her face in public.
Plans for our interview - the only one she is giving to a British newspaper - have been made with care. No photographs (those in circulation are years out of date), no voice recordings, only instructions to meet the publisher of her memoir, Judas, which sold 80,000 copies on the day it came out in the Netherlands and went on to top 500,000 in a country of just 17 million.
The book has since been optioned by Steven Spielberg and appears in translation in Britain and America this week.
I show up at the appointed hour and place, to be whisked on to another location where, in an otherwise empty meeting room, sits Astrid Holleeder. She has even brought cakes.
Wim served a prison sentence for his part in Heineken's kidnap, but a sizeable chunk of the £14 million ransom paid was never recovered and oiled a criminal empire that encompassed everything from gambling and prostitution to real estate and drugs.
Astrid had, she admits, long been aware of her brother's criminal activities, but they had taken place outside the family circle and somehow she put them to one side. She effectively lived a double life, bound by a Mafia-like family code of honour, building a career as a sensible solicitor - "moral" is her word - while serving as confidante for her brother.
It was her realisation that he was behind the 2003 hit on Van Hout, the fellow Heineken kidnapper married to their sister, Sonja, that finally led her to turn him in - believing her family would never be safe until he was behind bars for life.
"If my brother-in-law had shot my brother, I would have testified against him, too," she tells me.
She secretly made contact with the Ministry of Justice and in 2013 began co-operating with the Dutch authorities to make covert recordings of conversations with her brother in which he candidly owns up to his crimes.
Though there is eight years between them, Astrid and Wim were the closest of the four Holleeder siblings in a working-class home in the Jordaan, Amsterdam's working-class district.
Their father was a violent alcoholic (employed by Heineken) who terrorised them and their mother.
"Wim is the eldest and I'm the youngest and we had a particular bond. We look alike and we even speak in the same way," she says.
"I listen in court and hear us using the same phrases. I sometimes think, if I had been a boy, would it have been different, could I have been a killer, too?"
She gives evidence from behind a screen. "I cannot see him, he cannot see me. He knows how to threaten me with his eyes. He enters your soul. That is why it is so difficult to break the bond between us."
What she has always done is keep her own daughter, Miljuschka, now a well-known TV cook in the Netherlands, and her two grandchildren, 8 and 6, away from her brother.
"I know that if Wim really wants to hurt me, he will take out my daughter first. That is what I am most afraid of."
Yet Miljuschka herself takes no special security measures.
"I asked her when I made my decision to testify," says Astrid. "I gave her a choice that I wouldn't speak to the justice department. She has my spirit, and though she acknowledged the danger, she told me that sometimes you just have to do the right thing. Finally, I can tell the truth. In my family we have been keeping secrets for so long. It is hard to live with secrets. It interferes with all your relationships."
It certainly wrecked her partnership with Jaap Witzenhausen, Miljuschka's father; a kind, older man she chose as he was so unlike anyone she had known growing up, yet who was slowly ensnared by Wim into criminality.
"It is a very attractive lifestyle," she reflects without animosity. "People don't see it happening. They get infected; brain-washed."
She speaks as an observer, rather than a participant in her own life. The only time she breaks down during our two hours together is when I ask what she misses most about freedom.
"Going out with my grandchildren," she says, "going out with my daughter and enjoying what she has achieved. She was on a show called Dance, Dance, Dance [the Dutch version of Strictly Come Dancing] and all the other celebrities had their mothers with them in the audience and..."
Now the tears run messily down her cheeks.
She no longer believes her brother's conviction will save her: "He will kill me," she insists once again, without self-pity. "He says he can't live without doing it."
The only way out, she can imagine, is if Wim dies (he has had surgery for a heart problem in prison). "I love him, but I'd love him more if he was dead."
She shakes her head at herself.
"You should have hope, as a human being, that people can change, but he will never. He's not just damaged. It's biological. He is a psychopath."
The interview ends, I am escorted out and, when I look back, the room is empty, though I have heard no door open and shut.
Astrid emerged from the shadows and now they have reabsorbed her. It is almost as if she doesn't exist.
- Judas: How a Sister's Testimony Brought Down a Criminal Mastermind, by Astrid Holleeder, is published by Hodder & Stoughton
