N.Y. Civil Practice Law & Rules § 1002 (2026)

§ 1002. Permissive joinder of parties.  (a) Plaintiffs. Persons who
assert any right to relief jointly, severally, or in the alternative
arising out of the same transaction, occurrence, or series of
transactions or occurrences, may join in one action as plaintiffs if any
common question of law or fact would arise.
  (b) Defendants. Persons against whom there is asserted any right to
relief jointly, severally, or in the alternative, arising out of the
same transaction, occurrence, or series of transactions or occurrences,
may be joined in one action as defendants if any common question of law
or fact would arise.
  (c) Separate relief; separate trials. It shall not be necessary that
each plaintiff be interested in obtaining, or each defendant be
interested in defending against, all the relief demanded or as to every
claim included in an action; but the court may make such orders as will
prevent a party from being embarrassed, delayed, or put to expense by
the inclusion of a party against whom he asserts no claim and, who
asserts no claim against him, and may order separate trials or make
other orders to prevent prejudice.