CFR Member Henry Kissinger, CFR Past Member Jon Huntsman, American Patriot & Non-Member Of CFR Ron Paul sib·ling noun 1. a brother or sister. 2. Anthropology . a comember of a sib, a unilateral descent group thought to share kinship through a common ancestor. Murdered Polygamist Parley P. Pratt Is Great-Great Grandparent To Both Jon Huntsman & Mitt Romney.