Analysis of information sources in references of the Wikipedia article "Kayı (tribe)" in English language version.
As ethnographers testify, ethnically "pure" peoples do not and cannot exist. On the contrary, new peoples arise from ethnic mixes of two or more peoples, usually assimilating the best features of each. There are many folk legends that the beginning of a nation was laid by two (or several) brothers ... Apparently, something similar lies behind the legend of Kiy, Schek, Horev and Lybed. The tribal name Kyy (Kiy) belonged to the ancient Turkic peoples. It is still present in the names of tribal structures of modern Turkic peoples.
Огуз — одно из тюркских племен (кабиле), они же туркмены...Второй (род) — Кайыг/(Oghuz - one of the Turkic tribes (kabile), they are also Turkmens. Second (clan) - Kayig)