Louis and Zelie Martin, the parents of French saint - Therese of Lisieux, were canonized by Pope Francis in St. Peter's Square Basilica on Sunday. The Martins are the first married couple who became saints through the global church council on family.

"The holy spouses Louis Martin and Marie-Azelie Guerin practiced Christian service in the family, creating day by day an environment of faith and love which nurtured the vocations of their daughters," Pope Francis said during the mass.

According to the Pontiff, Louis (1823-1894) and Zelie (1831-1877) were "evangelists who opened their door" to those who seek help during a period when "a certain bourgeoisie ethic was contemptuous of the poor."

Initially, Louis intended to be a monk but was rejected for not knowing Latin well. He then met and fell in love with Zelie in Alencon, Normandy, whom he married three months later.

Louis and Zelie first planned to live as brother and sister but a priest was able to persuade them to have children.

Until today, the couple is considered as role models among Christian families for raising five daughters who became nuns. They had a total of nine children - four of which died at a young age.

Their youngest daughter, Marie-Francoise Therese Martin, was born in 1873 and became a nun at 15. Before her death due to tuberculosis in 1897, she wrote her autobiography, The Story Of A Soul, which is a memoir of how she dedicated her life to God after a troubled childhood following her mother's death.

Pope Francis shared that he carries one of her books in his travelling bag for help and guidance.

St. Therese of Lisieux was canonized in 1925 by Pope Pius XI who described her as "the greatest saint of the modern times". John Paul II then proclaimed her as doctor of the church in 1997 to honor her writings and preachings.