they don't know
Ustedes no conocen a mi hermano.
You don't know my brother.
They know no mercy.
Muchos europeos no conocen el Japón moderno.
Many Europeans are unfamiliar with modern Japan.
They don't know their neighbors.
Los niños pequeños no conocen muchas palabras.
Young children don't know many words.
Parece que muchas personas no conocen la diferencia entre"flojo"y"perder".
It seems that many people don't know the difference between “loose” and “to lose”.
Sea amable con la gente nueva, no conocen a nadie todavía.
Be kind to new people, they don't know anyone yet.