Kate Middleton was the first royal to wash her hands of the disgraced ex-Prince Andrew. The Princess of Wales refused to speak to Andrew at family functions and during holidays, Royal author Christopher Andersen told Page Six in a recent exclusive interview. “She is the first royal to cut him off, to turn her back on him,” Andersen, whose latest book is called “Kate! The Courage, Grace, and Power of the Woman Who Will be Queen,” explained. Kate Middleton was the first royal to shun the former Prince Andrew, a royal author claims. She is seen here with her husband, Prince William, at the requiem mass for the Duchess of Kent in 2025. WireImage Christopher Andersen, author of the biography, “Kate!” says that Middleton was the first to “turn” her back on Andrew. Page Six She also reportedly barred him from attending her Christmas concert at Westminster Abbey.…