The parents of St Thérèse of Lisieux are to be the first husband-and-wife couple to be made saints together.

Pope Francis approved the decrees permitting their canonisation just days after his document setting out the basis of October's Synod on the Family was published by the Holy See.

The double canonisation of this couple marks a celebration of their extraordinary marriage which led to the bith of "The Little Flower", St Thérèse, born in 1873 and who entered a Carmelite convent at the age of 15. She died at the age of just 24.

Cardinal Angelo Amato, prefect for the Congregation for the Causes of the Saints, said the canonisation of Louis and Zélie Martin, born Guerin, will testify to their "extraordinary witness of conjugal and familial spirituality".

The couple had nine children and just five survived into adulthood. All five of these entered religious life.

Father James Martin, Jesuit priest and author of My Life with the Saints, said: "The canonization of Louis and Zelie Martin is a reminder from the Vatican that married people are just as holy as - and often holier than - priests, sisters, brothers, bishops, cardinals and popes. And that a marriage is as much a road to holiness as a monastery."

When the couple were beatified in 2008, Father Martin wrote in intimate detail in the Wall Street Journal about their unusual marriage. After their wedding in July 1858 in France, they remained chaste for 10 months in what is known as a "Josephite marriage", so described after the marriage of Mary and Joseph.

Louis Martin had once hoped to become a monk and Zelie to be a nun. It was only after they were married and Zelie took them both off to see a priest that Louis was persuaded of the sacred nature of having children.

Most saints have been unmarried. The few who were married include Sts Peter, Monica, Thomas More and America's Elizabeth Ann Seton.