Drug Addict

A guy in need of advice. My ex just got engaged (today) to a known drug addict who was just arrested in July for possession and has a violent history (arrested and charged). Some background when I left her and moved on she flipped and accused me of child neglect and domestic violence. She had me arrested in which the case for domestic violence is still pending but the child neglect was dropped (even the CPS case was dropped after they just spoke to me on the phone). We have Court next week to determine my visitation and custody. Is there any way I can stop her Fiance from being around my kids? I honestly do fear for their safety and well being!

Side note: I don't want people thinking its just because she moved on and now I'm the jealous ex. I also don't want people thinking that I'm a hypocrite, the girl I moved on with is now my wife and we are expecting a child together. She has never been arrested or even accused of anything, if it wasn't for his violence and drug abuse I would encourage the relationship between them and my children.