"He no longer has strength. He is going through the natural process of aging, as am I," Georg Ratzinger said of his 85-year-old brother in the interview published in the ABC newspaper.

"My brother wants more tranquility for his old age. With the advance of his age, his strength is declining. It is a beneficial decision for the Church," the 89-year-old Ratzinger added.

The German-born Benedict last week shocked Catholics around the globe with his announcement he would step down on February 28, the first to resign voluntarily in 700 years.

"He had to face difficult tasks and did all he could. It is a decision that simply arose. It is the cycle of life and nobody will escape it," his brother said in a telephone interview from his home in Germany.

"I hope he will be remembered as a pope who strove with all his might to deepen and broaden the faith of the Church. And that he was an example of a life of a believer guided by faith."