Perhaps, theoretically, you could file a petition for third-party custody. Such a claim would be very highly unlikely to succeed.
Evidence is presented to a judge. Talk to a lawyer about this case. Write down your facts. It is up to the judge as to who to believe or not. You need a lawyer.
This response is only a basic answer to your question and is not intended to be legal advise. It is your job to hire an attorney and to discuss the specifics of this question with him or her. I am not giving you specific legal advise and there is no attorney-client relationship created by my answer to your question. The choice of an attorney is an important decision that you must make and that choice should not be made upon adverting alone.
Who are you to the child? Are you the father? Some other person? is there a custody order? We really don't have enough information to say anything more than "talk to a lawyer, make your case to a judge."
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