Kennedy, Jr., the son of assassinated politician Robert F. Kennedy, became embroiled in a bitter divorce and custody case with Mary after filing to end their 16-year marriage in May 2010.
He sought out an order of protection against his estranged partner last September (11) ""for the sake of my own safety and sanity"", telling a judge Mary was a trained boxer who was prone to fits of violence.
In his affidavit, obtained by Newsweek, Kennedy, Jr. told a judge Mary, who killed herself last month (May12), suffered from borderline personality disorder, threatened to commit suicide if he left her, and ran over his dog when he eventually moved out.
He even claimed to have once thrown himself out of a second-storey window to save himself after Mary lashed out at him in the middle of the night, and confessed to cheating on her to escape their marital woes.
Mary's relatives are fuming after the release of Kennedy, Jr.'s sealed 60-page affidavit, which they have branded ""nothing more than a brutal psychological weapon in the divorce case"".
A statement from the family reads, ""The affidavit, which Mary repudiated at the time, is full of vindictive lies. This latest piling on is proof perfect of the unbelievable emotional and psychological abuse that Mary endured during the last years of her life, and now in death.
""Our hearts are breaking for what her children continue to witness. We hoped Mary could rest in peace. There will be a time and a place for the true facts to come out.""
Mary was found dead aged 52 after hanging herself in her New York home on 16 May (12).