The explosion took place at the house of Mauji Lal and his brother Ram Narain in Tidua village in Yaqoobpur area under Bela police station area in the wee hours, police said.
The critically injured have been referred to a hospital in Kanpur.
Police said the houses of Mauji Lal, his brothers Ram Narain and Ram Sewak and neighbour Ram Autar were damaged under the impact of the explosion.
Four policemen, including in charge of Yaqoobpur police outpost Udal Singh, have been suspended and a case has been lodged against Mauji Lal and Ram Narain.