What are his rights as a legal immigrant father?

My boyfriend who is from Guatemala has three children from his separated wife. She has refused him on a number of times were he can not see the children, but yet she makes him pay $800.00 per month in child support. She has given so many excuses she is too tired to bring them over and refuses him to come get them. Her latest one is she needs to meet me and if she doesn't approve he will have to break up with me or never see his kids again. She has told him no one will help him because he is not from this country and they would deport him before they allow him visitation of his kids. So he pays the support she tells him to pay under the table and collect welfare and not reporting the child support. Any advise for us????