Family name Seong-Yun (성윤 
, Seong-Yun 
) , throughout the world, is a very rare last name. The cognomen Seong-Yun is habitual in Eastern Asia, particularly China, where it is an extremely rare surname. Much more frequently, Seong-Yun is the forename as well as the last name. Parts of the name also exists independently as a last name Seong, and a first name Yun.