Clerical sexual abuse scandals in the Catholic Church have led some to feel they can no longer trust the church's message, Archbishop Eamon Martin has said.
Archbishop Martin said the church faced a challenge in finding new ways of communicating "sincerely held perspectives" about the family.
The Archbishop of Armagh was speaking at the World Meeting of Families in Dublin, where he replaced US Cardinal Donald Wuerl as the keynote speaker.
The Archbishop of Washington pulled out of his scheduled appearance after he was criticised for his handling of child sexual abuse allegations in Pennsylvania.
Archbishop Martin said: "In the aftermath of child abuse scandals and other shameful episodes of the past, there are those who feel they can no longer trust our message, perhaps because they have been directly hurt and betrayed in their families by their experience of church, or because the revelations of such heinous crimes have shocked them to the core."
The All-Ireland Primate said Pope Benedict XVI had alerted the institution in 2010 to the fact that the sins and crimes of sexual abuse in the church have not only had tragic consequences in the lives of victims and their families.
Archbishop Martin told the gathering that the State must be encouraged to support the exclusive union between a married man and a woman as a "cherished" space for raising children.
He said: "We must work together with all people of goodwill to encourage the State to support the family, and especially the uniqueness of the faithful and exclusive union between a married man and a woman as a cherished space for the bearing and upbringing of children.
"In doing this, the State is not only caring for its citizens, but it is also strengthening and nurturing the foundations of society itself."
The archbishop added that the church was not suggesting that it wanted the State to overly intrude into, or replace, the important autonomy of the family.
But he said the church believed that if the institution of the family was harmed, then all of society suffered.
"The family is much more than an economic or social unit," he said.
"It is a privileged space for care, education, health promotion, mediation, security, community cohesion and safety."
Also speaking at the WMOF, Fr Sean Donohoe, co-director of Capuchin Day Centre in Dublin, said that the "enormous shortage" of housing in Ireland has left families sleeping on streets, tents and hostels in Dublin.
Pope Francis is to visit the centre on Saturday as part of his visit to Ireland.
Founded by Capuchin Brother Kevin Crowley, the centre provides 1,000 hot meals a day, clothing and showers to the homeless in Dublin.
Fr Sean said that while the centre cannot solve the homeless crisis, it could help ease the problem.
He was speaking at a panel discussion on homelessness entitled No Room At The Inn.
"There is an enormous shortage of housing in Ireland," he said.
"We have the homeless who are obvious to us, who sleep on our streets, in tents, in hostels and emergency accommodation and hotels.
"While there is no doubt there is a crisis, I'm also convinced there is a vibrant Christian response in our culture."
"We cannot solve the homeless problem in our country, we can help ease the situation for those who have nothing."
Conor Hickey, chief executive of Crosscare, a social support charity of the Catholic Archdiocese of Dublin, said that homeless families did not exist three years ago.
He said: "Traditionally homeless is associated with an individual who might have a number of problems.
"The current homeless crisis is defined by families and individuals who have no homes.
"Families who, through economic problems of no control of their own, found themselves struggling to find somewhere to live."
Thousands of pilgrims are expected to attend events for the WMOF, with 37,000 individuals and families due to take part in the pastoral congress in the RDS during the week, attending workshops, panel discussions and exhibitions.
Church urged to change tack on LGBT issues
Meanwhile, gay rights campaigners have called for the Catholic Church to remove its stigma against the LGBT community.
Launching the Equal Future campaign in Dublin to coincide with the beginning of the WMOF, campaigner Tiernan Brady said he wanted to highlight the damage being done to children and young people.
The campaign is the largest global initiative of LGBT groups, including 60 countries worldwide.
Mr Brady said there is a "clear message" that members of the LGBT community were not welcome at the event in Dublin.
"We want to highlight the damage that is being done to children and young people as they grow up thinking that to be LGBT would be wrong, a disappointment or just bad luck but none of those are true," he said.
"The sad truth is there is a clear message they are not welcome at the World Meeting of Families. LGBT looked to have stands and they were denied.
"Images of same-sex families were removed from all the material and I can't think of a clearer message to show LGBT people you are not part of this and you are not wanted in here.
"That's not what Catholic people feel and it's about time the upper management caught up with this.
"No child should ever grow up feeling they are less than others if they are or were to discern they are LGBT."
The founder and director of the Equality Campaign said that when the Synod of Young People takes place at the Vatican in October, he wants to raise awareness of that damage done to young people.
Mr Brady added: "The Synod on Young People is a once-in-a-generation moment for us to shine a light on the role stigma against LGBT in its various forms affects the mental health of children and young people, and has for too long been overlooked.
"It is important for the church to look at this as part of their stated desire to consider situations where young people face exclusion for social or religious reasons."
Additional Reporting Edel McAllister