Can my boyfriends ex girlfriend keep the kids from me?

Note that no true legal opinion can be given, but there should be no legal order.  Based on the little information given, it seems that you are a "legal stranger" to the children.  It would be as if anyone showed up at her residence offering to take the children to a movie.  They should not be allowed to go.  You would have no "right" to see them; and she would have no need to obtain any such order.  Practically, is a different story.  The Father was the Defendant of an OP; this proceeding was only dropped, not found to be without merit.  As such, she may be able to refile and obtain another OP that precludes him, when he is with you, from seeing the children. Also, it seems that your existence/relationship fuels the on-going fight, so, practically, the better option may be to take a low profile.  This matter does appear to be headed for court.  There are issues of visitation, support, and the like to be resolved.  There may also be [depending on your residency] mandatory mediation of the issues.  This may be an avenue worth exploring.  Accordingly, the suggestion is for you and the father to meet with an experienced family attorney to ascertain both your respective rights and any risk to those rights.  A first step would be to contact the local county bar association for a referral to such an attorney(s).