Mourners filled St Patrick's Church in Dundalk this morning for the funerals of Mark, Louise and Evan O'Connor who were found dead at their home in Co Louth last week.
Cian O'Connor paid tribute to his mother, father and younger brother Evan at the ceremony.
He said: "I know for many of you here today, what has happened is difficult to understand and put into words. No words can truly reflect how we all feel, how I feel, I'm hurting. We all are.
"It's something that may take an age to come to terms with, and a part of each of us may never heal. However, while it's difficult to comprehend, it's not something that we should ignore or forget or allow to overshadow the wonderful lives of my family.
"Instead, my family would want to celebrate the rich lives they led, to remember the good times and to remember the memories they left behind."
The bodies of 54-year-old Mark, 56-year-old Louise and their 27-year-old son Evan were found at the O'Connor family home in the Drumgowna area last week.
Cian also thanked the local community for the support they had shown to the family over recent days.
He said: "I want to thank everybody here for being with us in this extremely difficult moment in our lives. The outpouring of support from you all has been immense. We've felt it to our very core. So thank you."
After the heartfelt tribute, Cian received a round of applause from those gathered in St Patrick's Church.
During the Prayers of the Faithful, thanks was given for Mark, Louise and Evan's "unique gifts" while Cian and Robert O'Connor were prayed for along with members of the extended family.
Fr Gerry Campbell, the administrator for Louth parish, was the chief celebrant.
The priest said the outpouring of love for the family has been "extraordinary".
The joint funeral mass was also concelebrated by a number of priests from surrounding parishes, including the parish priest of St Patrick's Church, Fr Mark O'Hagan.
Members of the North East Runners Athletics Club in Dundalk, of which Mark was a member, lined the way as the three hearses and funeral cortège made their way into the church grounds this morning.
Many mourners were wearing odd socks at the request of the family "in honour of one of Evan's individualistic traits".
Several family members brought forward a number of items to the alter as symbols of the lives of Mark, Louise and Evan.
The items for Mark included: runners, a medal and a Boston running book; a record by the band Queen; and a cook book.
The items for Louise included: a record from the band A-ha and sheet music from her choir; a cat collar; and a photo depicting her work as a nurse.
The items for Evan included: a holiday photo book; odd socks (tied in a knot, the last pair he tied in a knot himself); a swimming cap; and a model train from the Thomas the Tank Engine show.
In his homily, Fr Campbell said Mark, Louise and Evan had been "united in love".
He said: "What shines through every memory, every message, and every tear is the deep love that Mark and Louise had for each other, and the boundless love they both had for Evan - their son, their joy, their pride, and their world."
Paying tribute to Mark, Fr Campbell said he was a "man of quiet integrity, of deep conviction, and of steady purpose."
He said: "Mark knew what it meant to labour - not just in his work, but in his calling to justice and compassion.
"Whether it was through Inclusion Ireland, advocating for people with disabilities, or co-founding the ABACAS School, Mark gave himself completely for the good of others."
Fr Campbell said Louise had "cared for others with gentleness and humour, bringing comfort and joy to the people she met, whether in hospitals, or at the VHI call centre, or among friends in her beloved Local Vocals Choir".
He added: "And above all, she loved Mark and Evan with every part of her being.
"She and Mark were soulmates, having first met in secondary school. She being a Saint Louis Girl, and he a De la Salle boy, two years her junior - they were partners in life and in service - a couple whose love overflowed into action, especially in their care for Evan and in their advocacy for other families living with autism."
Speaking about Evan, Fr Campbell said "his joy was pure," "his smile could light up a room" and "his love was unfiltered and wholehearted".
Fr Campbell said: "When we think of Evan - his love of holidays, of swimming, of his colourful odd socks and bright tee-shirts. His love of Thomas the Tank Engine.
"His joy in going to the Hub Praxis in Drogheda, his love of theme parks, aqua aerobics, going with his Dad to the Park Runs…in all of this we see a young man who brought light and joy to those around him."
Before finishing his homily, Fr Campbell appealed for greater supports for mental health services.
He said: "Given that Mark devoted his life to advocating for the disability sector and for those in need, it would be remiss of me not to echo his spirit and appeal for greater care, compassion, and resources for mental health in our nation.
"We cannot bring them back - but we can honour them by ensuring that no other family has to walk this road alone," Fr Campbell added.
A private cremation service is to take place following the funeral mass.
Robert O’Connor, 31, of Drumgowna, Louth Village, appeared before a special sitting of Drogheda District Court this day last week charged with three counts of murder.
The court was told that he had been with mental health services since the age of 22 and an application was made for him to receive the appropriate psychiatric assessment.
