Are you going through a divorce? Is there an Order giving the father custody? Please contact an attorney so that you can discuss your situation and get legal advice that is appropriate to your situation.
You should contact a Family attorney and file a motion in court to set the terms of custody. If this has already been done and the father was given sole custody, then you can always file a motion (preferably through your attorney) for modification.
THESE COMMENTS ARE NOT LEGAL ADVICE. They are provided for informational purposes only. Actual legal advice can only be provided after consultation by an attorney licensed in your jurisdiction. Answering this question does not create an attorney-client relationship or otherwise require further consultation.
Unfortunately, your inquiry doesn't provide many details about how the children came to reside with their Father. However, my office offers free initial telephone consultations if you would like to discuss this matter in more detail, as well as explore the potential rights and options available. If you would like to coordinate a free initial telephone consultation, please contact my office at 407-971-6140 to schedule same.
Please note that this response is not intended to create any attorney-client relationship and is only based on the limited facts given. The response might change should additional facts be learned and should not be relied on as legal advice. It is recommended that you consult with an attorney who can properly assess the situation, as well as all pertinent facts, prior to taking any action based on the foregoing statements.