The area police boss Gladys Ogonda says the suspect confronted the two siblings accusing them of engaging in an affair.
Ogonda says there has been a long standoff among the trio over the alleged love affair which the suspect had termed a curse to the family.
She says the suspect stabbed the two in different locations using a kitchen knife.
The suspect is said to have first walked into his uncle’s house and stabbed him severally in the stomach before locating his aunt.
The suspected killer’s father is a brother to the deceased siblings.
Ogonda says the suspect fled the scene on Thursday morning as police launched a manhunt.
Villagers said the suspect might have escaped to Tanzania to evade arrest while the bodies have been taken to Migori District level four mortuary.