The victims were named locally on Monday night as Marcella Wilson (in her 40s ), who lived in Belmullet, her seven-year old son, Sean, and her mother Mary Ann Wilson.
The crash involved an artic truck & two cars on the Mallow Rd in Cork.
Two women and a seven-year-old child were killed after a auto and a truck collided on the N17 Galway to Sligo Road near Claremorris at around 12:30pm.
Two people, believed to be American tourists, have been killed in a crash near Blarney, while three others, including one child, were killed in a crash near Claremorris, Co.
The two people who died were passengers in a hire vehicle that was in collision with a truck. The driver of the truck was uninjured.
Both are understood to have been visitors from the USA who were travelling in Ireland with their partners.
They were being treated at Cork University Hospital and their injuries are described as non life-threatening.
Gardaí are appealing for witnesses to contact Claremorris Garda Station on 094-9372080, The Garda Confidential Line on 1800-666-111 or any Garda Station.