Charles Spencer, brother of the late Princess Diana, is no stranger to writing books about British kings. ‘Swan Song: Diana, My Sister,’ which will be published on September 22, is his take on his sister's life and her unhappy marriage to the now King Charles. In pre-released excerpts, Spencer claims Charles was ‘giddily elated’ in the aftermath of Diana's death in 1997, reopening a painful episode for the royal family ↧ Princess Diana's brother, eyewitness to history, sparks royal ruckus Charles Spencer, brother of the late Princess Diana, is no stranger to writing books about British kings.