How Can I Initiate a Conversation with Someone Who Thinks He’s a Christian but Isn’t?

Questions about initiating conversations with someone who thinks he’s going to Heaven but who isn’t showing any signs he’s following God, how to talk to unsaved friends and family who identify as Christians, and resources to help someone learn what true Christianity is.

How can I initiate a conversation with my brother who thinks he’s going to Heaven because he has an intellectual belief that Jesus is the Son of God, but who doesn’t really show any signs that he’s following God?

How would you suggest talking to friends or family who identify as Christians despite strong evidence they’re merely nominal or cultural Christians?

Are there resources I can share with my brother that will help him learn what true Christianity is?