New York Consolidated Laws, Domestic Relations Law - DOM § 5. Incestuous and void marriages

1. An ancestor and a descendant;

2. A brother and sister of either the whole or the half blood;

3. An uncle and niece or an aunt and nephew.

If a marriage prohibited by the foregoing provisions of this section be solemnized it shall be void, and the parties thereto shall each be fined not less than fifty nor more than one hundred dollars and may, in the discretion of the court in addition to said fine, be imprisoned for a term not exceeding six months. Any person who shall knowingly and wilfully solemnize such marriage, or procure or aid in the solemnization of the same, shall be deemed guilty of a misdemeanor and shall be fined or imprisoned in like manner.