Hi i'm looking for advice on a situation, last weekend my children came home from their fathers and one of my children informed me that my ex's brother in law was smoking in the back of his car with our children in the car, my son said the smoke got in his face but his dad claims that he didn't know his brother in law was smoking though he himself is a smoker and has always had the car strictly no smoking zone with the kids in the car. Since our seperation he has been glued to his brother in law and sisters hips and anything they do is never wrong. Well our children are also getting tired of visiting daddy and having to spend time with his whole family and not just with him. My son was then made out to be a liar about the smoking thing so i felt quite angry about this and have told their dad that if he sees our children then his family do not see them, i feel i cannot trust him with my children and i can't trust his family. this same person also smokes cannabis in his own house with his children inside, I don't want my children around this person and i don't know what to do because i know he won't do as i ask and not have the children around him. I need some advice on best to deal with this because i don't want to stop him seeing his kids but i feel like i can't trust any of them with my children anymore.