1. Without rituals there can be no Hindu marriage. A marriage performed without rituals has no legal recognition.
2. If your brother married his second wife before the judgment of the court whereby his first marriage was declared as void then he has violated the law. Your brother is accordingly liable to be prosecuted and punished for remarrying in spite of being already married.
3. That your brother's second wife is a patient of schizophrenia does not carve out any defence for your brother.
4. The affidavit signed by his wife can be used in the court to show that she was aware of the first marriage.
5. Since you have moved the High Court the only suggestion we can make is to continue your case and hope for the best.