God doesn't deal with us like this, and it would be wrong for you to conclude that your brother died because God somehow wanted to punish you. It's true that God may have lessons to teach you through your brother's death—but that isn't why he died.
I suspect that down inside you feel very guilty over the way you treated your brother—and these feelings of guilt have convinced you that God must be punishing you for your neglect. Your guilt is real; you should have done more to bridge the gap between you, no matter what the causes were. But what should you do with your guilt? To put it another way, what does God want you to do with it? Does He want you to carry this burden forever?
The answer is no! Instead, God wants you to bring your burden of guilt to Him and let Him take it away—not just your burden over the way you treated your brother, but the burden of all your sins. God loves you; He loves you so much that He sent His only Son into the world to die for your sins.
The Bible says, "Here is a trustworthy saying that deserves full acceptance: Christ Jesus came into the world to save sinners" (1 Timothy 1:15). By faith turn to Christ and ask Him to take away your sins—and He will. Then ask Him to help you to love others and show compassion to them instead of neglect.