Chastity Bono, the daughter of Cher, is having a sex change to become a man.
A spokesman for Bono, born a girl to Cher and Sonny Bono, says the author "has made the courageous decision to honour his true identity" and began the process of changing sex earlier this year.
Publicist Howard Bragman said Bono (40) was proud of his decision and hoped "that his choice to transition would open the hearts and minds of the public regarding this issue".
The writer, activist and reality-TV star came out as gay 20 years ago.
In the book Family Outing, Bono describes feeling "somehow different -- specifically different from who my mom expected me to be".
Bono's second book, The End of Innocence: A Memoir, details how relationships with Joan, a lover, and her parents changed after coming out.
In 1995, Bono posed for the cover of the gay magazine The Advocate.