Mohinder (42), his wife Babli (40), daughter Usha (14), sons Sanjay (11) and Rajesh (9) consumed poison in an attempt to commit suicide at their residence, they said.
The victims were rushed to hospital where Usha and Babli died during the treatment.
However, the rest of them were shifted to PGIMS at Rohtak under critical condition.
Another daughter of Mohinder, Tamanna had gone mysteriously missing in February this year and was still untraceable, due to which the family was under tension, leading them to take the extreme step, police added.