U2 frontman Bono has revealed a family secret – he has a half-brother, whose existence he did not know until he became an adult.

"I have another brother, whom I love and adore, who I didn't know I had," the 62-year-old singer told BBC Radio 4's "Desert Island Discs" ahead of the release of his new memoir, "Surrender: 40 Songs, One Story."

The rockstar shared that his mother, Iris, who died in 1974 when he was 14, never knew that her husband had an affair with a woman close to the family.

"It's a very close family and I could tell my father had a deep friendship with this gorgeous woman, who's part of the family, and then they had a child. And this was all kept secret. Nobody knew," Bono said in the interview Sunday.

After discovering the truth about the half-brother in 2000, Bono spoke to his father before he died in 2001.

"I asked him, did he love my mother, and he said yes," Bono said on the radio show. "And I said, how could this happen, and he said, 'It can,' and that he was trying to put it right. He wasn't apologizing, he was just stating, these are the facts. And I'm at peace with it."

The truth left Bono with feelings of regret.

"I am sure I was hard to deal with. He was coping with other stuff in his life. He was very droll and very funny. But it got rough," the "With or Without You" singer admitted. "I feel like I wasn't there for him."

Bono also offered a formal apology to his deceased father while at a chapel in France.

"There was nobody there, I lit a candle and I got on my knees and I just said, 'look I'm sorry I wasn't there for you, you went through a lot and please forgive me' and I felt free."

Bono's memoir is set to be released on Nov. 1. It will cover the singer's early days in Dublin, including the death of his mother, the success of U2 and his activities supporting the fight against AIDS and poverty.

Bono belted out U2 classics from the platform of Kyiv metro station
Bono belted out U2 classics from the platform of Kyiv metro station AFP / Sergei SUPINSKY