Your brother's situation deeply saddens me, and I know it saddens you -- because it didn't need to be this way. Frankly, your brother believed a lie: that he could live any way he wanted to and put off giving his life to Christ until the very last minute. But apparently that "very last minute" has come and gone -- and now it's too late. The Bible warns us not to delay our decision for Christ, because "Now is the time of God's favor, now is the day of salvation" (2 Corinthians 6:2). We never know how much -- or how little -- time we may have.
But your brother believed another lie also: that following Christ is dull and boring, and the only way to be happy and enjoy life is to live for yourself and the pleasures of this world. But it isn't true! Yes, sin may give us temporary pleasure -- but in time it passes, and we're left empty and bored and unfulfilled.
Jesus promises us another way, however -- a way of joy and peace, because it is God's way. Jesus said, "I have come that they may have life, and have it to the full" (John 10:10). I pray that every person reading your letter will take it to heart, and not delay making their decision for Christ. Don't gamble with your eternal soul!