Namesakes
Islamic Caliphs:
2 caliphs
Caliph Osman II (a.k.a. Usman) 1618-1622 Ottoman 
Caliph Osman III (a.k.a. Usman) 1754-1757 Ottoman
Other Leaders:
1 president
President Shehu Shagari (a.k.a. Usman) 1979-1983 Nigeria
Ottoman Sultans:
2 sultans, 1 bey
Bey Osman I (a.k.a. Usman) 1281-1326
Sultan Osman II (a.k.a. Usman) 1618-1622
Sultan Osman III (a.k.a. Usman) 1754-1757