In French, the verb has to agree with the subject, that's why there are several verb forms.
être: je suis / tu es / il, elle, on est, nous sommes, vous êtes / ils, elles sont
In English, it's similar: I am / you are / he, she, it is / we are / they are
Not sure about Chinese, but it Japanese, there is only one verb form for all subjects for a given tense, so maybe that's where the confusion is coming from.