Shreedhar Shetty killed his son Saidhar (5) and daughter Shraddha (9), before hanging himself, Thane District Rural Police said.
According to police, Shetty's wife was allegedly having an extra marital affair and had left him, while he lived with the two children in Ganesh Complex in Nala Sopara.
Disturbed over his wife's affair, he killed his two children and then hanged himself from the ceiling at his residence late last evening, police said.
Police suspect that the children were poisoned.