English grammar rule Have part agreement
Personal pronouns are the subject of the clause, and can be in the first person (I, we), the second person (you), or the third person (he, she, it, they). They are either singular (I, you, he, she, it) or plural (we, you, they). The form of the verb must match the form of the personal pronoun.
Incorrect They makes a happy family. Correct They make a happy family. Incorrect He paint the house when it look shabby. Correct He paints the house when it looks shabby.