There are two Hadiths that I recently came across:
‘A’ishah reported: Ibn Umm Maktum was the mu'adhdhin of the Messenger of Allah (May peace be upon him) and he was blind. Sunan Abi Dawud 535
Allah's Messenger (ﷺ) said, "Bilal pronounces the Adhan at night, so keep on eating and drinking (Suhur) till Ibn Um Maktum pronounces the Adhan." Sahih al-Bukhari 620
Did Masjid e Nabawi have two Muezzins during the Prophet's lifetime simultaneously? If yes, why were two azaans given for Fajr prayer in Ramadan for the same jamaat?