The arrested have been identified as Ramu, a resident of Balsamand in Fatehabad district, and his paramour Praveena.
The duo had killed Puneet (8) and Payal (7) on July 13 and dumped the bodies in Bhattu canal, police said.
During interrogation, Ramu told police that he had killed the children on suspicion that his wife was having an extramarital affair and her paramour had fathered the kids.
After killing the children, Ramu stayed with his wife for few days and then eloped with Praveena, police said.