 He is the son of an officer in the Janissary corps, Süleyman Ağa, who died during a campaign to Pécs.Mehmed Çelebi himself was enrolled in the Janissary corps, and since he had served in the 28th battalion (""orta"" in Janissary terminology) of the corps, he came to be known with the nickname "Yirmisekiz" ("twenty-eight" in Turkish) for his entire life.His descendants, including his son who became a grand vizier, also carried the name in the form of "Yirmisekizzade" ("son of twenty-eight").