According to the book I am reading now, a relative clause ending with noun must be followed by の. But sometimes I also find a relative clause ending with noun that is followed by である.
Consider the following examples:
A: 両親が日本人の学生はクラスの20%をしめている。
B: 両親が日本人である学生はクラスの20%をしめている。
Literally it means
The students whose parents are Japanese constitute 20% of the students in the class.
Questions
When do we have to use の and である for a relative clause ending with a noun?
Is there any difference in nuance?