Just as some people are kind and thoughtful and can be depended on to help whenever they're needed, unfortunately others are almost the exact opposite. Not only are they selfish and inconsiderate, but they also take delight in being malicious and hurtful.
I often think in this connection of King Manasseh in the Old Testament. He had every advantage; his father, Hezekiah, was one of the most spiritual kings the ancient Israelites ever had. But Manasseh turned away from God, rejecting everything his father believed and embracing instead every evil practice imaginable -- including child sacrifice. The Bible says he not only was an evil man, but he also deliberately led the whole nation into evil.
But Manasseh's kingdom was overthrown by another nation, he was captured and put in prison. And while he was there, Manasseh did something no one could ever have expected: he turned to God. The Bible says, "In his distress he sought the favor of the Lord his God and humbled himself greatly" (2 Chronicles 33:12). As a result, God forgave him, and also gave him a second chance by restoring him to his throne. Afterward, Manasseh demonstrated his change of heart by reversing his evil policies.
What is the point? Simply this: God can forgive and change even the most evil person. Pray for your cousin, that God will break through the hardness of his heart and show him his need of Christ. And pray too that you may be an example to him of Christ's love and mercy.