Probably some African ethnic groups. I'm thinking constituent groups of Nigeria and Ethiopia may be larger. Also if you consider African descended groups in the Americas as separate groups then the USA and Brazil have higher African slave descended populations than Kurds are. (Honestly even some White groups in North America may be larger but few people set them apart other than maybe French Canadians. There is more intermarriage among North American Whites (other than French Canadians) than interracial or Kurds with others)