Students and lack of respect

So someone very close to me is a male teacher who teaches islamic studies

There is one boy in the class (its a segregated class) who is borderline disrespectful

Because its borderline i think the teacher just lets it slide but that boy doesn’t act that way to other teachers which I have noticed

It hurts me not only because the teacher is a family member & it boils my blood to see them disrespected this way but also because there are students who want to study the Deen at an advanced level yet lack the basic adab for the teacher and it scares me because soon they will graduate & call themselves a scholar all the while having rotten morals

Everytime im in class on the inside im raging whenever an incident happens & sometimes im close to making dua for this ‘student’ to be humbled real bad because he thinks he is a top guy

But then i wonder if im being too biased because of the personal relationship I have with the teacher (as in theyre family to me)

But sometimes i cant even concentrate in class & i harbour bad feelings for this student

I dont really know how to approach the teacher either in a respectful way to as to not hurt their feelings either