What Can I do?

My sisters boyfriend was accused of Murder. He was later aquitted as the judge deemed it was not his fault, but he went to prison for manslaughter. He was Paroled 10 years ago, and his risk esment was 5, the highest is 35. The media had a field day, they published things that were inaquate and they were told by the Judge to stop spouting this rubbish as it is untrue, unfortunately, by the time he went to court, the public believed him guilty as charged and they still do. My wife wont allow me to take my children to visit my sister, because he could be there. Morally and If I did not know the truth, I would agree, but can she do this. Her father is a prison warden at the prison he served and even he said that he doesn't approve. My wife and I have split up and she wont now let my kids stay with me overnight for this reason, I'd move, but I have no where else to go. What can I do and could she or her father get into trouble