I am sorry to hear what these kids are going through. When you say that there is an open case against the Mom, do you mean that there is a DFCS case against her in Juvenille Court? There are some circumstances where you can intervene in these cases for Temporary or Permanent Guardianship. If the Father intervene's, however, your rights will be secondary to his. Since the parents are still married, it makes your case that much more difficult.
Without knowing what the open case is it is hard to say what you may be able to do. I'd advise going to a local attorney and bringing all the information with you so he or she can more effectively assess your options.
Father and grandma need to have a united front on behalf of these children. Father could petition for divorce in the superior court and grandmother could intervene in the action to seek temporary custody or permanent custody depending on the circumstances. There are other options in the juvenile or probate court, but if divorce is imminent, figuring out the issues alongside of that seems to be the most efficient means to resolve the issues. Residency requirements for divorce are the same in both GA and FL-6 months. Georgia requires that the petition for divorce be filed where the defendant resides, but Florida allows filing in the county where either party resides. I'm guessing mom is still in Georgia and any potential witnesses relating to the neglect issues would be in Georgia, so it seems it would be more beneficial for the children in terms of determining custody and parenting time. If dad is not going to be in GA any time soon and there is concern about mom swooping in at any time and collecting the children, I would suggest going through the either the juvenile or probate court for other options. See the attached link for further explanation. Good luck and best wishes for the children.
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