Georgia law permits someone to file in court as a "next friend" of a minor child if he or she has no legal guardian or other representative. Whether this applies is difficult to tell based on your description. You should consult with a family law attorney to understand whether you will be able to do this, or if there are other proceedings already under way. Please call 770-753-9995 for a no cost 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.