Khloe Kardashian's brother allegedly confronted Lamar Odom about cheating rumours.

The 29-year-old reality TV star's younger sibling, Rob Kardashian, got into a heated exchange with his brother-in-law of fours years, who was recently accused by a second woman of having an affair.

A source told gossip website ''Rob confronted Lamar and it got heated very, very quickly. Rob and Lamar have been close since he came into Khloe's life.

''When Rob asked Lamar point blank if he had cheated on Khloe with criminal defence attorney, Polina Polonsky, he refused to answer the question. Rob grew angrier that Lamar didn't respond, and he ended up just leaving the house. A lot of people bash Rob, but he truly has his sister's back, and is very protective of her.

''Rob has been continuing to stay with Khloe, and has been a big source of support for her at this very difficult time.''

Rob moved in with Khloe and Lamar shortly after they got married and is very close with the basketball star.

Khloe reportedly kicked Lamar out of their house ''after the most recent reports about Lamar's affair with Polina became public.''

A family insider added: ''Khloe and Lamar are talking daily, but he isn't allowed back in the house.''