The siblings- Gandhi Jeroy and Madhu Jeroy- aged 19 and 21 years, and hailing from Odisha, were arrested, while their brother-in-law is at large, police said.
The three are accused of beheading and bobbitising Biranchi Manjhi, who also hailed from Odisha.
Police said the brothers and the victim werestaying together at Doddathogur near Electronic City here.
A few months ago, the brothers learnt about the alleged illicit relationship. The brothers along with their brother-in-law allegedly killed Manjhi on September 10, police said.
Police tracked the accused with the help of sniffer dogs.