Can parents with black eyes have baby with blue eyes?

My brother and his wife have brown eyes, both, but they have 2 doughters with blue eyes.
Of course that is very strange, because my mother and his wife mother have green eyes.
So, hos his doughter can have blue eyes?
Who know to explain this, and in your family do you have situations like this? My mother have green eyes, and my father brown, but i have green eyes like my mother, and my father brown, as my fathed had. so, is normal, we have our parents eyes color.
Why his doughter have blue eyes?