The lesson in this story is to be responsible and file for paternity BEFORE something like this happens. Had you filed for paternity before she moved, you'd have had a clear right to object to her moving more than 50 miles. Now, most judges would agree that, she you haven't had yourself legally declared the father, she had a right to move the kids. You can still file for paternity, though, although you are behind the 8-ball in terms of getting a judge to order the kids back to Miami.
The contents of this answer should be considered friendly advice, not legal advice (I'm a pretty friendly guy), and the answer should not be construed to constitute an attorney-client relationship. Also, if you liked this answer as much as my big ego thinks you did, be sure to click the thumbs-up button!
Paternity hasn't been adjudicated so there isn't much you can do until it is. File a petition asap so that paternity is established and a time sharing arrangement and child support obligation can be established. Until doing so you have no rights to the children. You should also register with the putative fathers registry immediately.
You should file a paternity action right away. The more time that passes, the less likely you are to get a judge to agree that the children should be returned to Miami. Under the law, since you did not have a custody order in place and were never married to the mother, the mother is considered the natural guardian of the children and therefore has the right to custody and sole decision making at this time. The way to assert your rights is through a paternity action in which you establish your custody right and your right to make decisions affecting the welfare of your children (i.e. where they will live, go to school, etc.). Best of luck to you.
An attorney-client relationship shall not be formed due to the response to the asked questions. The suggestions made are intended to inform and not advise and are based upon general statements of PA or FL laws as applicable and specific events or facts may alter the law. You should contact an experienced PA or FL family law attorney (as applicable) for specific legal advice regarding your issue.
Based on the limited information provided, you need to file a paternity action in Miami and it is advisable that you do so immediately. Also is is unclear if there is a prior judgment of paternity with regards to your kids. I strongly recommend you contact an attorney in Miami at your earliest convenience to address your case.
Good Luck with your case.
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