Aatish, the sole surviving member of the family, who were found murdered on Thursday in Preetam Nagar under Dhoomanganj police circle in Uttar Pradesh's Prayagraj, has been arrested for masterminding the killings.
His friend Anuj has also been arrested, while two other accused are still absconding.
According to the police, Aatish masterminded the murder of his father Tulsiram, 64, mother Kiran, 60, sister Niharika, 30, and wife Priyanka ,25, because they had been opposing his relationship with a maid servant.
During interrogation, Aatish claimed that when he returned from some work, late on Thursday afternoon, he saw the blood-soaked bodies of his family members.
ADG Zone Prem Prakash said locals were questioned and CCTV footages in the area were scanned to identify suspects.
It was during investigations that the police learnt of the dispute in the family over Aatish's relationship with the maid.
Aatish was detained and during interrogation, he confessed to having hatched the conspiracy. He had given a contract for killing for Rs 8 lakhs and his friend Anuj had arranged for the killers who are still at large.
ADG Prem Prakash has announced a reward of Rs 50,000 for the team that cracked the case.
( With inputs from IANS )