동생 dong-saeng: younger brother/sister (when you address a younger sibling you call their name). Dongsaeng is a Korean word describing a family or friendship relationship. It is used to refer to one's younger sibling or a close friend that is younger than oneself. "I promised my dongsaeng I'll treat her for dinner if she did well on her test." "Dongsaeng, make me a cup of coffee."