The Pope has called for prayers not "gossip" to enable the synod on the family to take place successfully in Rome in October.
The Archbishop of Westminster Cardinal Vincent Nichols has also called on priests not to take the debates over the synod to the press, after the Catholic Herald ran a letter from nearly 500 clergy calling on the Church to hold the traditional line on controversial issues such as homosexuality and communion after divorce and remarriage.
Pope Francis said conversion and reconciliation was possible, however sinful a family had become.
He repeated his often-made call for inclusion, saying the Church should be dedicated and united in the witness of the truth of God's love and mercy for the families of the world, with none "excluded", whether "inside or outside" the flock.
Prayers, "not gossip," are needed for the synod, and "I invite even those who feel distanced or those who aren't used to it to pray," he said at his weekly audience, Catholic News Service reported.
He said the bond between church and family is "sacred and inviolable" and the church "is solemnly committed to taking care of the family."
Pope Francis said: "The church, as mother, never abandons the family even when it is disheartened, wounded and demeaned in so many ways, not even when (the family) stumbles in sin or distances itself from the church."
Cardinal Nichols said every priest in England and Wales had been asked to reflect on the synod. "Pope Francis has asked for a period of spiritual discernment. This dialogue, between a priest and his bishop, is not best conducted through the press."
In the letter, published in the Catholic Herald, more than 460 priests wrote: "We wish, as Catholic priests, to restate our unwavering fidelity to the traditional doctrines regarding marriage and the true meaning of human sexuality, founded on the word of God and taught by the church's magisterium for two millennia.
"We commit ourselves anew to the task of presenting this teaching in all its fullness, while reaching out with the Lord's compassion to those struggling to respond to the demands and challenges of the Gospel in an increasingly secular society," the letter continued.
"Furthermore we affirm the importance of upholding the church's traditional discipline regarding the reception of the sacraments, and that doctrine and practice remain firmly and inseparably in harmony."