During his trip to Fatima, Portugal in May, Pope Francis will make two of the three shepherd children believed to have seen a vision of the Madonna 100 years ago there saints, the Vatican said on Thursday.
Millions of faithful each year visit the Fatima shrine, one of the most famous in Christianity.
The canonization of Francisco Marto and his sister Jacinta Marto will take place in Fatima on May 13, to coincide with the 100th anniversary of the reported apparitions by the two and the third visionary, Lucia Dos Santos.
Francisco and Jacinta died while they were still children several years after the visions. Dos Santos became a nun and died in 2005 at the age of 97.
The Catholic Church posthumously confers sainthood on people considered so holy during their lives that they are now believed to be with God and can intercede with him to perform miracles.
Miracles are usually the medically unexplained healing of someone. The miracle connected to the siblings was believed to be the inexplicable healing of a Brazilian infant whose parents had prayed to the siblings but the Vatican has given no details.
Francisco and Jacinta Marto were beatified - the last step before sainthood - by Pope John Paul in 2000. The beatification process for Dos Santos began after her death in 2005.
The Church believes that the Madonna gave the children three messages, the so-called three secrets of Fatima.
The first two were revealed soon and concerned a vision of hell, seen by believers as a prediction of the outbreak of World War Two, a warning that Russia would "spread her errors" in the world, and a need for general conversion to God and a need for prayer.
The "third secret" intrigued the world for more than three-quarters of a century, inspiring books and cults convinced that it predicted the end of the world.
In 2000, the Vatican said the third secret was a prediction of the 1981 assassination attempt on Pope John Paul on May 13, the same day of the first reported apparition in 1917.