Many people rewrite their wills several times over the course of their lives. What you should do A legal document called a codicil can amend your current will. However, it is often simpler just to write an entirely new will. Codicils can be tricky and can lead to contests of your will in court.
Wills are matters of public record.
Therefore, when you die, your nephew can view your original will, view the codicil, see he's been cut out, and decide to challenge the will in court. Work with an experienced lawyer in your state. An amendment to your will.