Proceed to obtain an order on consent from the Family Court pursuant to a custody petition. Use or at least consult a family law attorney to do it most efficiently and correctly.
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File a petition with the Family Court in your county. By going to the Petition window in the courthouse, a clerk will be assigned who will assist you in filing out the application and explain the procedures for serving her. Then on the court date (usually about 4-6 weeks later) the Judge can generally give you a custody order if the mother is consenting. In any event, for a full assessment, I'd advise to schedule a consultation with a NYC Child Custody lawyer.
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