How to delete parent object when last associated child is deleted?

I have a Family model that has_many Kids. I'm using dependent: :destroy on the family so when it is destroyed the associated kids are destroyed too. All good.

Now I need to destroy the family when the last associated kid is deleted. This is to prevent stray families in the database that have no kids.

Should I do it in students_controller#destroy method? Or is there a better way?

I have a similar case as well. Is there some rails magic available for that ? :)