You must protect your right to custody by filing the proper pleadings and having an experienced custody attorney representing you. Do not attempt to do this alone. If they have not named you as a party in their complaint for custody (this is not done by motion, although they may have filed an emergency motion in the pending custody case), then you need to intervene in the case. See an attorney immediately.
I am exclusively a family law attorney, practicing primarily in the metro Atlanta, Georgia trial courts. However, I handle appeals from anywhere in Georgia.
In Georgia, the law favors parents over third parties such as grandparents. However, you must do something promptly or there will be no one to oppose the grandparents and you may lose by inaction. Troxel is not a state case, so you can't rely upon the favorable language there. Beyond that, the facts will make a great difference, so please speak with an attorney. We routinely handle custody and grandparent rights cases, so please feel free to call for a no-obligation evaluation.
I am providing general information on the law only, and no attorney-client relationship exists by virtue of this exchange. You can not rely upon this as formal legal advice. If you require specific legal advice, you must hire an attorney and then your communications will be protected by attorney-client privilege, and you will have the benefit of an opinion of counsel.
I agree with Attorney Zezima. You must act to protect your rights. Since you have a custody order which spells out your custodial rights, you must assert those rights in order to protect them. You have the right to custody in the event the custodial parent is unable to provide for the son, to the extent that the custodial arrangements is in the best interest of your son. There is a presumption that it is, but, the grandparents can challenge that concerning you. They have a higher burden of proof where the parents of the child are concerned, but they can prevail. As Mr. Zezima said, do not try this alone. You need very skilled representation to intervene in the case immediately. And, don't assume that by just showing up you can contest their petition. It really doesn't work that way and there is a lot of ground to cover and a lot to do to prepare to meet there claim, head on.
This information is of a general nature and is not intended to be relied upon as legal advise. You are encouraged to contact and discuss your matter with an experienced attorney to more specifically address your legal needs.