incesttuous
In*cest"tu*ous, a. Etym: [L. incestuosus: cf. F. incestueux.] Defn: Guilty of incest; involving, or pertaining to, the crime of incest; as, an incestuous person or connection. Shak. Ere you reach to this incestuous love, You must divine and human rights remove. Dryden. -- In*cest"tu*ous*ly, adv. -- In*cest"tu*ous*ness, n.