Nine year old twin brothers Thomas and Patrick O'Driscoll were stabbed to death by their older brother Jonathan in their Deerpark home on the outskirts of Charleville.
The 21 year old's body was discovered shortly after the incident in a woodland area in the nearby town of Buttevant.
He is believed to have been struggling with mental health issues and had taken his own life.
The Cork County Coroner is due to hear the inquests in Mallow today.
