To file a suit for custody of the children, you must have standing. If you had actual care, control, and possession of the children for at least six months ending not more than 90 days preceding the date of filing, you may file a petition for custody. Note that you must file within 90 days of the date the children moved out of your home. If you are a grandparent or another relative, you may be able to file for custody if the children's present circumstances would would significantly impair their physical health or emotional development.
You may be able to file the suit for custody in your county of residence, if the children have not yet been in Alabama for six months.
You really need to sit down with an attorney and explore the facts and your options.