My fiancé and her kids and her ex husband. me being around them.

My fiancé has 2 kids(3 and 5 years old). Which i support and take care of like they are my own. I love them like they are my own. Her ex husband is saying he has a temporary order thats states i cant be around the children because he doesnt like me. He states that i cant be around them and told my fiancé(his ex wife)(mom of the kids) that she is not to let them see me or let them be around me. i was wondering if he can do that? And if i would be served with a paper or something stating this? And if the wife would have to agree or sign a paper that has to do with the citation? Please let me know as soon as possible. Im staying away right now because he scared her and she isnt letting me see them but she wants me to still be in there life. We both appreciate it. Thank you.