N.Y. Relig. Corp. Law § 220
Two or more unincorporated churches, which separately agree on a plan of union and determine to meet together for the purpose of being incorporated as a union church, may be incorporated as a union church in pursuance of the provisions of article ten, and thereafter such union church shall be governed by the general provisions of such article, as near as may be, except as otherwise provided in this article. A notice of such joint meeting shall be given to the congregation of each church, in pursuance of the provisions of article ten of this chapter, relating to notice of meeting for incorporations, in every respect as if it were a notice of a meeting for the separate incorporation of such church under such article, except that the notice shall state in substance that a joint meeting of such unincorporated churches, which shall be specified in the notice, will be held for the purpose of incorporating such churches as a union church, and electing trustees thereof at a time and place specified in the notice, which place may be the usual place of worship of either of such churches or any other reasonably convenient place. Such notice must be signed by at least six persons from each of such churches who would be authorized to sign a notice for the meeting of each church, respectively, for the purpose of incorporating it under such article.
The provisions of article ten hereof shall be applicable to the organization and conduct of such meeting, the matters to be determined upon and the certificate of incorporation to be executed and filed accordingly, except that the presiding officer of such joint meeting shall be the oldest person present at such meeting who would be entitled to preside at a meeting of either of such churches singly for the purposes of incorporation in pursuance of such article. All persons who would be qualified to vote at such meeting of either of such churches held singly, shall be qualified voters at such joint meeting, and the number of trustees of the union church after incorporation, to be selected from each such church, may be agreed on by such unincorporated churches, and the trustees shall be selected by each of such churches accordingly.
The certificate of incorporation shall set forth the plan of union agreed on and the number of trustees of the incorporated union church to be selected by each unincorporated church.
N.Y. Relig. Corp. Law § 220