After killing mum Miryam Kowalczuk, 50, and stepdad Ricardo Klein, Leandro Acosta had sex with their dead bodies.
The 25-year-old then chopped up the rest and fed them to their family’s six dogs.
The twisted man claims his stepsister Karen Klein – who is also his lover – helped dispose of the bodies.
Acosta’s lawyer said he carried out the torturous act because Klein had abused him and his sibling.
Police are convinced his lover and stepsister Karen helped him.
The pair justified their unthinkable actions saying that the dead couple had started to abuse their twins which they have together.
They said the matter had been reported to the police who failed to do anything about it.
Only then they insist they were forced to take the law into their hands.
The killings took place at the family home in Pilar in the province of Buenos Aires, Argentina.
The victim’s brother Roberto Klein said there was a lot of tension between stepdad and stepson.
“My brother was a difficult man, with little time for his children, there has always been resentment between him and his stepson and I believe this was a long time coming,” admitted Roberto.
Acosta’s defence lawyer, Monica Chirivin, added: “He does not feel remorse and in fact describes a state of relief for a burden he has felt since childhood.
“He told me that he ate a bit of the corpse. For him it was almost a pleasure.”
The crime came to light when a victim’s relative contacted police after being refused entry into the family home.
Police discovered pieces of a female pelvis and vertebra column in an old paint pot.
Karen said her stepbrother shot his stepdad while he was asleep and later shot his mum in the head as she walked in the door.
