God is able to do what we can't do, and that includes working in another person's life to convict them of sin and draw them to Christ. The Bible says, "The prayer of a righteous person is powerful and effective" (James 5:16).
And that's why I urge you to keep praying for your brother, even if nothing seems to change. After all, you don't know everything that's going on in his heart; down inside, doubts may be arising about the way he's living -- doubts caused by the work of God's Spirit. Or God may be using your prayers to keep him from even greater harm. From time to time I get letters from people who've prayed for a spouse or other loved one for many years -- and are rejoicing because their prayers have finally been answered.
Also, do all you can to keep contact with your brother -- not to lecture him (which he'd probably resent), but simply to let him know you care. Your love could be an example to him of Christ's love.
At the same time, ask God to give you opportunities to talk with him about the life he's living and where it's likely to end up. Above all, seek to point him to Jesus Christ, who loves him and yearns for him to become part of His family forever. The Bible says, "Let your conversation be always full of grace, seasoned with salt, so that you may know how to answer everyone" (Colossians 4:6).