Can a person with schizophrenia live their entire life without telling anybody?

The reason I’m asking is because we suspect that my brother is schizophrenic but is unwilling to tell anybody. He has been on antidepressants for a couple years now but he hasn’t worked or had a social life for long before the antidepressants. He has a lot of the symptoms of schizophrenia. He talks to himself and a lot of the things he says don’t make any sense. He can sometimes sit and stare at a wall for hours without doing anything. He passes back and forth in his room sometimes. We told his doctor about what we suspected but when the doctor asked him if he hears people talking to him he said no.

I’m just wondering if a person who has schizophrenia can chose not to tell someone because that would mean that they know they are sick right? We just don’t know how to help him because he is always very detached from everybody.