Gänswein assures that face infection is "painful but not serious."
Biographer reports that his voice is frail, though his mind is sharp and he is feeling optimistic.
Pope emeritus offers profound reflection on role of faith in culture.
Longtime secretary, Archbishop Georg Gänswein, reads Benedict's words at funeral Mass for Georg Ratzinger in Regensburg
Francis notes Benedict XVI's consideration in informing him of the news first.
He had just celebrated his 69th anniversary as a priest.
Pope Emeritus went to his homeland to visit his ailing 96-year-old brother.
After four days with his ailing brother, the pope emeritus will be back home in Rome.
Pope Emeritus in Regensburg with Georg Ratzinger, 96
The first portion of the biography is expected in English in November.