At the height of his fame, the "Rocky" star reached a confidential multimillion-dollar settlement with his half-sister over the abuse allegations, reported New York Post.
Sources close to the star insisted the settlement was the result of a "shakedown" and that Stallone, 66, was a victim of blackmail.
Papers obtained show Stallone agreed 26 years ago to give his half-sister USD 2 million plus USD 16,666.66 per month for her lifetime, plus a trust with USD 50,000 per year for psychiatric and medical expenses.
According to the papers, Filiti "asserted claims for personal injury, including physical injury" against Stallone, who "vigorously denied and continues to deny and dispute all claims of wrongdoing."
Filiti died in August last year from lung cancer at age 48.
Jacqeline, mother of Sylvester and Filiti, says the settlement was the result of blackmail by Filiti, whom she described as a pillpopping drug addict desperate for cash.
"This was nothing more than a shakedown. Toni-Ann was on 65 Oxycontin pills a day, and she threatened Sylvester. A drug addict will do anything. When Sylvester became famous, she didn't have to hook. He was trying to help her. He caved in," she said Wednesday.