Has he ever mentioned who is his psychiatrist? If he has you may want to contact the office and let them know. They won't disclose anything nor should you ask but simply say, this man who told me he is your patient wrote me this email and I think you should be aware of it. He may not be getting the right level of treatment. You might also want to talk to your local social services department as they would be able to step in and offer him more support or assistance with his mental health. I would not contact his sister or mother as you don't know the history between them.