( CNN ) -- Pope Emeritus Benedict XVI will attend the Mass of canonization of John Paul II and John XXIII , the Holy See confirmed Saturday , according to Vatican Radio . Benedict XVI , who will be attending at the invitation of Pope Francis , will not be at the altar , but will figure among the cardinals and bishops . It wo n't be the first time Benedict has made a public appearance since taking the almost unprecedented step of resigning the papacy . He was also present for a ceremony in February in which Francis created 19 new cardinals . Since a new pope usually takes the reins only following the death of his predecessor , seeing both him and Francis together remains a highly unusual event . The two canonization candidates share an improbable path to sainthood : they both rose from very humble beginnings to lead the Roman Catholic Church . John XXIII ( 1881-1963 ) -- known as Angelo Giuseppe Roncalli before he became Pope -- was one of 13 children born into a family of Italian peasants , farmers from a tiny village in the country 's north , before being sent away to study for the priesthood at age 11 . John Paul II ( 1920-2005 ) , born Karol Jozef Wojtyla , was brought up in a grimy industrial town in Poland and raised by his soldier father after his mother died when he was just 8-years-old . He spent his formative years living under first Nazis , then Communists . His beatification is the quickest in modern times , made possible because Benedict -- who succeeded John Paul in 2005 -- waived the normal five-year waiting period after death to get someone 's beatification rolling . Vatican spokesman Father Federico Lombardi said as many as 150 cardinals and 1,000 bishops would attend the canonization ceremony , as well as 24 heads of state , Vatican Radio reported . The ceremony is also expected to draw upward of a million pilgrims , who will gather in St. Peter 's Square to witness the two former popes enter the celestial community of Catholic saints . CNN 's Laura Smith-Spark , John L. Allen , Jr. and Daniel Burke contributed to this report .
Pope Emeritus Benedict XVI will attend the canonization of John Paul II and John XXIII . Vatican says as many as 150 cardinals and 1,000 bishops expected to attend ceremony . As many as a million pilgrims are expected to witness the event in St. Peter 's Square .