Shiva's 19-year-old married sister had apparently started talking to her ex-lover over phone after coming to her parents' home, they said.
The accused saw her conversing with her paramour and in a fit of rage killed her with knife, police said.
He was sent to a juvenile home in Moradabad yesterday following the order of Rampur Juvenile Court, district police chief Sadhna Goswami said.
In a similar case, a 25-year-old married woman killed her paramour and his wife in Safini area here as she was upset over his marriage with the other woman.
The S P said the deceased was involved in an illicit relationship with a married woman and started staying with her along with his wife.
A case has been registered against the woman, her son and two daughters, he said, adding the four were sent to jail yesterday.
