( CNN ) -- Three of the best-loved leaders in the history of the Roman Catholic church will be united this weekend when Pope Francis makes his predecessors , Pope John XXIII and Pope John Paul II , saints in a special ceremony in St Peter 's Square . 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 the age of 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 eight . He spent his formative years living under first Nazis , then Communists . For both boys , the church offered a way out -- and up . `` Roman Catholicism , unlike temporal power , has been one of the most effective social elevators on this planet , '' says church historian Alberto Melloni , `` taking people from the most humble positions and bringing them to the top . '' Vatican analyst Robert Mickens says the pair 's poor backgrounds gave them a `` pastoral sense '' which was key to their success in the church -- and which goes some way to explaining their huge popularity . `` They did not come from noble families either one of them , [ but from ] working class families and I think they also were two people who had a real sense of humanity . '' The pair also turned out to be leaders with unforeseen qualities . John XXIII , already 76 when he was elected pope after a long career as a priest , professor and Vatican diplomat , had been expected to serve merely as a `` papa di passaggio , '' or interim , caretaker Pope . But instead , 100 days into his reign he took the surprising -- and courageous -- decision to try to shake up the church , calling for the Second Vatican Council ( better known as Vatican II ) , which he hoped would modernize Roman Catholicism , bring unity and improve its relations with other faiths . John Paul II , once an actor , had a presence before the cameras that enthralled millions of Catholics young and old as he evangelized to the far ends of the earth . It 's not what he might have expected , growing up under not one but two dictatorial regimes . Both men were much loved by the Catholic faithful -- in their final days , masses were held for them around the globe , while thousands of people crowded into St Peter 's Square to offer prayers . When John XXIII 's death was announced , the crowds wept for `` Il Papa Buono '' ( `` The Good Pope '' ) ; more than 40 years later , when John Paul II died , thousands cried `` santo subito ! '' ( `` Make him a Saint now ! '' ) . It did n't happen right away , but John Paul II 's canonization did come sooner than tradition would usually dictate . For John XXIII also , the rules have been changed ; he is credited with just one miracle , rather than the two which would usually be required for him to `` qualify '' as a saint . The pair 's double canonization is unprecedented : it will be the first time two Popes have been made saints on the same day . Experts say that in recognizing the two men together , Francis may be looking to heal a long-term rift in the church , dating back to Vatican II , that ground-breaking conference of church leaders set up by John XXIII . Karol Wojtyla -- who was to become John Paul II , but back then was simply a young bishop -- was at those meetings . He argued against John XXIII 's planned `` aggiornamento '' ( `` updating '' ) and was in favor of keeping with tradition . The modernizing Pope -- already gravely ill when the meetings began -- died before the event could reach the conclusion he had hoped for . The splits have remained ever since . Cardinal Paul Poupard , former president of the Pontifical Council for Inter-religious Dialogue , who knew both men , says Pope Francis is hoping to repair that rift by canonizing the two men who have come to represent the two opposing views . `` The pope is going to bring together in one ceremony the father of the council and [ the one ] who put it into action , '' he explains . For Cardinal Walter Kasper , former president of the Pontifical Council for Promoting Christian Unity , the double canonization is a sign of the church 's future direction . `` It 's official recognition that these were good popes and we will follow their steps now , '' he says .
Pope John XXIII and Pope John Paul II to be made saints in special ceremony . Pair -- and Pope Francis , who will canonize them -- are three most popular pontiffs . Comment: Commentators say Francis may be looking to heal rift within church .