Before revision: John M. Goggin and William C. Sturtevant (1964) listed eight societies which generally allowed sibling marriage, and thirty-five societies where sibling marriage was permissible among the upper classes (nobility) only.
After revision: John M. Goggin and William C. Sturtevant (1964) listed eight societies which generally allowed sibling marriage, and thirty-four societies where sibling marriage was permissible among certain classes only.