C. Lalramzauva (39), the younger son of one of the victims Lianngenmgi (76), confessed that he murdered his family members on Monday night.
Lalramzauva told the police that he committed the crime after his elder brother, Vanlalbela and their family members objected to his proposed marriage to his lover.
The family members objection was due to the fact that his girl friend was a divorcee, having three children and a drunkard, police said.
He further told the police that he used a small axe to commit the crime and the broken safe was to mislead the investigators as there was no money inside.
Three members of a family Lianngengi (76), her son Vanlalbela (50) and grandson Chhakchhuakthanga (11) were found dead in Tawipui North village in south Mizoram's Lunglei district on Tuesday morning