Nick Cave felt “disgracefully self-indulgent” following the death of his two sons. The 66-year-old rocker lost his son Arthur, 15, in 2015, when the teenager fell from a cliff near the family home in Brighton and he suffered further grief seven years later when his son Jethro, 31, died and Nick has now admitted he spent years wrapped up in his own ego and the double tragedy made him see the “folly” of his ways. During an appearance on ‘Australian Story’, he explained: “For most of my life I was just sort of in awe of my own genius … I had an office and I would sit there and write every day a…