New books "My brother the Pope" oby Georg Ratzinger, the brother of Pope Benedikt XVI. are presents in a books store in Regensburg, southern Germany, on September 13, 2011, ahead the book presentation with Georg Ratzinger in Regensburg. - AFP Photo

BERLIN: Pope Benedict XVI's brother, the Rev. Georg Ratzinger, says in a new book that his younger sibling never changed as he climbed the ecclesiastical ladder to the Vatican.

The 270-page ''My Brother the Pope'' was released in German on Tuesday.

The 87-year-old Ratzinger – a former choirmaster – says he and his brother have always been close.

He says that when they studied theology together in Freising, their fellow students came up with nicknames for them. The future pope was dubbed the ''book-Ratz'' and he was called the ''organ-Ratz'' because of his interest in music.

News agency dapd reports the book is written by historian Michael Hesemann based on hours of interviews with Ratzinger.