Mr and Mrs O’Connor actively campaigned for better services for autistic people in their community.
In 2003, they were among a small group of parents who helped to set up Drogheda Abacas Special School in County Louth and Evan was one of its first pupils.
On its Facebook page, staff at the school paid tribute to the family, expressing the “deepest sadness” over their deaths.
“Evan attended Abacas for 14 years. He grew up with us,” the school said.
It added that Mr and Mrs O’Connor were “passionate advocates for their son Evan and for all autistic people”.
“They campaigned, lobbied and fundraised for the school and youth clubs and will always be remembered for their legacy to Abacas and to autistic people.”
It said Mr O’Connor was also a board member of Autism Support Louth and Meath and worked as a “professional advocate for the rights of people with disabilities”.