Singer Bono believes it was the death of his mother when he was just 14, which inspired him to form rock band U2 and become one of the biggest rock stars in the world.

The U2 frontman's mother Iris died from a brain aneurysm four days after collapsing at her father's funeral in September 1974. Her death left a "hole" in his heart, reports femalefirst.co.uk.

"I realised aged 14, when my mother suddenly passed away at her own father's graveside, that I had a hole in my heart," the 55-year-old musician told The Sun newspaper.

To deal with his grief, Bono turned to music and that turned into his life.

He said: "I didn't know at the time, as I filled it with music. I became an artist through her absence and I owe her for that. I thought the rage I had was a part of rock 'n' roll but the rage was grief."

Members of the rock band U2 (L-R) David Evans aka The Edge, Larry Mullen Junior and Paul David Hewson aka Bono wait prior to the UEFA Champions League football match Monaco vs Arsenal, on March 17, 2015 at Louis II stadium in Monaco. Photo: AFP