Can I keep someone away from my children if I feel their safety is a concern?

If you truly believe she may be a threat to your children you can petition the court for an order prohibiting from being in the presence of the children during his visitation. However, my experience has shown the courts usually require there to be an actual threat, not just a concern that something happen.

Only if you go to court and ask for a modification of the present custody order.

First, understand that you alone do not have the right to impose your will *unilaterally* on your ex-husband as to who he can or cannot expose the children to. Just because you fear for the children's safety if the children are in the presence of a certain person or persons, you do not have the right to dictate to your ex-husband who the children can associate with when the children are with him and his friends or family members. Second, there are clearly times when an ex-spouse or parent of children that you have in common may not exercise good judgment and may in fact expose the children to contact with people that mean them harm or who will harm them inadvertently. In those situations, you have many options. If you no more strongly believe your children are in danger if and when your ex Ranger children into contact with a particular person or persons, you can request a child protective order through the juvenile court, and/or you can request what is known as a temporary restraining order or TRO. Both TRO and a child protective order our orders that you can obtain quickly and without notice to your ex (if the court believes that the children are in immediate danger). Protective orders and TROs only last for a limited period of time, however, so if you want to seek a permanent order for the protection of your children, you can also petition the court to modify the child custody and/or parent time orders to ensure that your ex-spouse's supervised when exercising parent time to ensure that he does not expose them to danger or dangerous influences.

If there is evidence of your claims, you should ask the court for orders to protect the children. I suggest you hire a lawyer.