Question: Who is Yujiulü Nagai's paternal grandfather?
Sentence (from "Kaya Alp"): Kaya Alp was, according to Ottoman tradition, the son of Kızıl Buğa and the father of Suleyman Shah, who was, in turn, the grandfather of Ertuğrul, and the great grandfather of the Ottoman Empire founder, Osman I.
Relevant evidence: No