VATICAN CITY (AP) — First, Pope Francis married 20 couples to highlight the role of families as the heart of the Catholic Church. Next up is a special Mass for grandparents.

Francis and 100 elderly priests will celebrate a Mass in St. Peter's Square on Sept. 28 in honor of the elderly, part of his long-standing belief that old people shouldn't be shut away in retirement homes but should be actively cherished for their wisdom.

Some 40,000 people from 20 nations are expected to attend. Francis plans to give each one a copy of the Gospel of Mark, written in large-sized type, said Monsignor Vincenzo Paglia, head of the Vatican's family office.

Paglia said Tuesday that one of the elderly couples taking part in the Mass recently fled the Islamic militant crackdown in northern Iraq and would recount their story to the crowd.

Francis was particularly close to his own grandmother Rosa. He has also said having Emeritus Pope Benedict XVI, 87, in the Vatican was like having a "wise grandfather" living at home.

The Mass for grandparents, and the group wedding that Francis celebrated last weekend, are aimed at focusing attention on family life ahead of a major two-year church study on family issues starting Oct. 5.

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