Mehmed I
Mehmed I (1379 – 26 May 1421), also known as Mehmed Çelebi ("the noble-born") or Kirişçi (from Greek "Kyritzeslord's son"), was the Ottoman Sultan from 1413 to 1421.
The fourth son of Sultan Bayezid I and Devlet Hatun, he fought with his brothers over control of the Ottoman realm in the Ottoman Interregnum (1402–1413).
Starting from the province of Rûm he managed to bring first Anatolia
and then the European territories (Rumelia)
under his control, reuniting the Ottoman state by 1413, and ruling it until his death in 1421.
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.
Guillaume Wittouck
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He was the Grandfather of industrialist Paul Wittouck.
Fujiwara no Nagara
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He was the grandfather of Emperor Yōzei.
Bayezid I
Bayezid I ((nicknamed Yıldırım (Ottoman Turkish: یلدیرم), "Lightning, Thunderbolt"); 1354 – 8 March 1403) was the Ottoman Sultan from 1389 to 1402.
He was the son of Murad I and Gülçiçek Hatun.
He built one of the largest armies in the known world at the time and unsuccessfully besieged Constantinople.
He adopted the title of Sultan-i Rûm, Rûm being an old Islamic name for the Roman Empire.
He decisively defeated the Crusaders at Nicopolis (in modern Bulgaria) in 1396, and was himself defeated and captured by Timur at the Battle of Ankara in 1402 and died in captivity in March 1403, triggering the Ottoman Interregnum.
Lyon Cohen
Lyon Cohen( 1868–1937) was a Polish- born Canadian businessman and a philanthropist.
He was the grandfather of singer/ poet Leonard Cohen.
Abd al-Muttalib
Abd al- Muttalib Shaybah ibn Hashim( c. 497 – 578) was the grandfather of Islamic prophet Muhammad.
Prithvipati Shah
Prithvipati Shah( ?–1716) was the king of the Gorkha Kingdom in the Indian subcontinent, present- day Nepal.
He was the grandfather of Nara Bhupal Shah.
Henry Bryant (naturalist)
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He was the grandfather of Henry Bryant Bigelow.
John Westley
Rev. John Westley( 1636 – 78) was an English nonconformist minister.
He was the grandfather of John Wesley( founder of Methodism).

Question: Who is Mehmed I's paternal grandfather?
Answer: Murad I