Hi,
why are thy exceptions? What's wrong?
Oh, are you referring to "they"? In that case, it's often used as a singular pronoun when you don't know someone's sex, so it's usually used with "someone", "no one", "anyone", etc. Some people don't accept that "they" is used that way, and will tell you it's wrong and you should use "his or her" instead, especially in formal contexts.
Was that what you were worried about?