Family name 三男 (Mitsuo 
, 三男 , Sannan 
) , all over the world, is quite a common surname. The last name 三男 is habitual in Lebanon, where it is quite a rare surname, Japan, and Norway, where it is a rare surname. Measured by absolute frequency, it is commonest in Japan, China, and Lebanon. Also, 三男 is the forename as well as the last name.