New York Laws
Part 1 - Substantive Rules Governing Dispositions
2-1.3 - Adopted Children and Posthumous Children as Members of a Class

(a) Unless the creator expresses a contrary intention, a disposition
of property to persons described in any instrument as the issue,
children, descendants, heirs, heirs at law, next of kin, distributees
(or by any term of like import) of the creator or of another, includes:
(1) Adopted children and their issue in their adoptive relationship.
The rights of adopted children and their issue to receive a disposition
under wills and lifetime instruments as a member of such class of
persons based upon their birth relationship shall be governed by the
provisions of subdivision two of section one hundred seventeen of the
domestic relations law.
(2) Children conceived before, but born alive after such disposition
becomes effective.
(3) Nonmarital children. For the purposes of this paragraph, a
nonmarital child is the child of a mother and is the child of a father
if the child is entitled to inherit from such father under section 4-1.2
of this chapter. The provisions of this paragraph shall apply to the
wills of persons dying on and after September first, nineteen hundred
ninety-one, to lifetime instruments theretofore executed which on said
date are subject to the grantor's power to revoke or amend, and to all
lifetime instruments executed on or after such date.