New York Real Property Actions & Proceedings Law Section 1511 - Additional parties.

  1511.  Additional  parties.  1.  In  an  action  brought under this
  article, the person in possession shall be made a party to  the  action,
  and  when  such person claims the right of possession, or an interest in
  the real property, under another, such other person shall also be made a
  party.
2. Where it appears to the court that a person  not  a  party  to  the
  action  may have an estate or interest in the real property which may in
  any manner be affected by the judgment, the court, upon  application  of
  such  person,  or  of any party to the action, or on its own motion, may
  direct that such person be made a party.

Last modified: February 3, 2019