How can i find out about visitation with ny niece's who are with their father while the mother (my sister) and him are goin through a custody battle?

You might be able to file for visitation. But you should use a lawyer since they already have a pending case. Above answer and comments to questions are for general purposes only and does not constitute legal advice or establishes an attorney-client relationship without a signed retainer. Please reach out to an attorney you are comfortable with working and discussing your case in more details. If you can not afford a private attorney, you may be eligible for a Pro Bono lawyer provided by some courts and if not, feel free to ask about our affordable payment plans.