The man had been prohibited four days earlier from approaching the family home.
Police are currently trying to reconstruct the hours leading up to the incident.
It is alleged that the child’s mother was returning home in her car after taking the other two children to their afternoon activities.
As she approached the house, her husband emerged and got into a car which he then used to ram her own.
The boy was found dead in the house which had been set alight.
The man was later arrested by police in a bar on a highway in Cremorna.
