N.Y. DOM Law § 76-E

§ 76-e. Simultaneous proceedings. 1. Except as otherwise provided in\nsection seventy-six-c of this title, a court of this state may not\nexercise its jurisdiction under this title if, at the time of the\ncommencement of the proceeding, a proceeding concerning the custody of\nthe child has been commenced in a court of another state having\njurisdiction substantially in conformity with this article, unless the\nproceeding has been terminated or is stayed by the court of the other\nstate because a court of this state is a more convenient forum under\nsection seventy-six-f of this title.\n 2. Except as otherwise provided in section seventy-six-c of this\ntitle, a court of this state, before hearing a child custody proceeding,\nshall examine the court documents and other information supplied by the\nparties pursuant to section seventy-six-h of this title. If the court\ndetermines that a child custody proceeding has been commenced in a court\nin another state having jurisdiction substantially in accordance with\nthis article, the court of this state shall stay its proceeding and\ncommunicate with the court of the other state. If the court of the state\nhaving jurisdiction substantially in accordance with this article does\nnot determine that the court of this state is a more appropriate forum,\nthe court of this state shall dismiss the proceeding.\n 3. In a proceeding to modify a child custody determination, a court of\nthis state shall determine whether a proceeding to enforce the\ndetermination has been commenced in another state. If a proceeding to\nenforce a child custody determination has been commenced in another\nstate, the court may:\n (a) stay the proceeding for modification pending the entry of an order\nof a court of the other state enforcing, staying, denying, or dismissing\nthe proceeding for enforcement:\n (b) enjoin the parties from continuing with the proceeding for\nenforcement; or\n (c) proceed with the modification under conditions it considers\nappropriate.\n