New York Consolidated Laws, Real Property Actions and Proceedings Law - RPA § 903. Necessary defendants

1. Every person having an undivided share, in possession or otherwise, in the property, as tenant in fee, for life, by the curtesy or for years;

2. Every person entitled to the reversion, remainder or inheritance of an undivided share, after the determination of a particular estate therein;

3. Every person who, by any contingency, is or may become entitled to a beneficial interest in an undivided share in the property, provided that where a future estate or interest is limited in any contingency to the persons who shall compose a certain class upon the happening of a future event, it shall be sufficient to make parties to the action the persons who would have been entitled to such estate or interest if such event had happened immediately before the commencement of the action;

4. Every person having an inchoate right of dower in an undivided share in the property;

5. Every person having a right of dower in the property, or any part thereof, which has not been admeasured;  and

6. An executor or administrator, where letters testamentary or of administration have been issued on the estate of the decedent from whom the plaintiff's title to the real property is derived, and the action is brought within eighteen months after such letters were issued;  or where the person of whose estate the executor or administrator has been appointed should, if living, be a party to the action.  If no executor or administrator has been appointed for the estate of such a person, that fact must be stated in the complaint.