Family Law Questions? Ask a Family Lawyer Online.
If there is no court ordered custody, but both parents are listed on each of the children's birth certificates, then either parent has the right to custody, and there is nothing that one parent can do to prevent the other from assuming custody.
If there is a court order for custody, then the order controls.
For a family law attorney referral in your jurisdiction, see: http://www.abanet.org/legalservices/lris/directory/ and www.martindale.com.
I sense there is more going on here, so feel free to elaborate.
Hope this helps.
Custody issues are the most contentious. You can go in without a lawyer, but unless the other parent does the same, you probably will lose.