Siblings Edward, Dominic, Marie-Nicole and Aldo Cascio are suing the late King of Pop's estate after alleging that Jackson "groomed and brainwashed" them when they were minors.
In a legal complaint obtained by PEOPLE, the siblings allege they met Jackson through their father, who worked at a luxury hotel visited by the late star.
They claim Jackson went on to supply them with drugs and alcohol, expose them to pornography and abuse them.
The complaint alleges: "Michael Jackson was a serial child predator who, over the course of more than a decade, drugged, raped and sexually assaulted each of the plaintiffs, beginning when some were as young as seven or eight.
"The filing alleges that the abuse occurred over extended periods in multiple locations worldwide, including during visits when Jackson and his children stayed at the siblings' family home."
Attorney Marty Singer, who represents the Jackson estate, told PEOPLE in a statement that they deny all allegations against Jackson and called the lawsuit "a desperate money grab by additional members of the Cascio family who have hopped on the bandwagon with their brother Frank, who is already being sued in arbitration for civil extortion".
He went on: "The family staunchly defended Michael Jackson for more than 25 years, attesting to his innocence of inappropriate conduct. This new court filing is a transparent forum-shopping tactic in their scheme to obtain hundreds of millions of dollars from Michael's estate and companies.
"Statements by the Cascios, including those appearing in dozens of passages throughout Frank Cascio's 2011 book, as well as in interviews with Oprah Winfrey and others, directly contradict what is being alleged now. Throughout, the Cascios consistently and repeatedly asserted that Michael never harmed any of them or anyone else.
"With the Estate's financial success growing, the Cascios, through two different attorneys, threatened to go public with heinous accusations that completely contradicted their previous statements defending Michael unless his Estate paid staggering sums of money."
Michael Jackson died on June 25, 2009, at age 50 from acute propofol intoxication.
His personal physician, Dr Conrad Murray, was convicted of involuntary manslaughter in 2011 for administering the lethal dose to treat insomnia.
He went on to serve two years out of a four-year prison sentence.
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