We, Koreans make plural nouns by adding "들" to nouns.
ex) 강아지 (puppy) -> 강아지들 (puppies)
However, we seldom use the plural nouns as it is clear in most cases whether the noun is singular or plural from context.
When we say, 'she has two kids', you know the noun, 'kid' is plural even though we do not change it to a plural form, kids.
So, we usually do not say, 그녀는 두명의 "아이들"이 있다 but we say, 그녀는 두명의 아이가 있다 instead.