How may I pray for my brother who committed suicide, asking Allah to forgive him, knowing that he was a very virtuous and well-mannered person?

Suicide is a grave and major sin, one of the greatest enormities. However, if the person who committed suicide had good deeds, perhaps Allah will forgive him for them. It is narrated in a hadith (definition) that a man emigrated with Tufayl ibn 'Amr al-Dawsi to Medina. He fell ill and became distressed, so he cut his finger joints and died. Tufayl saw him in a dream in a good state, with his hands covered. He was informed that he had been forgiven because of his emigration, but he was told: "We will not mend what you have spoiled." When Tufayl recounted this to the Prophet, peace and blessings be upon him, he said: "O Allah, and for his hands, forgive!" Therefore, supplicate for him often, seek forgiveness for him, and give charity on his behalf.