The thing is that Ranvir has always been very protective and loyal towards his family. Despite the fact that Sahil was a total loser, Ranvir would not whup him like that...
Also, as someone else mentioned, Sahil is definitely not dead. Because his body was unidentifiable, in TV land, it means that it's not him. It's an old trick to have some of Sahil's personal belongings next to the body... simply put, Sahil isn't dead!
Also, a lot of effort was put into transforming Ranvir into a good guy. Now he is established as a guy who cannot do wrong... therefore it would be tough to justify a sudden and extreme negetive turn like this.
I'm convinced that Ranvir is not guilty at all... but as I said before, it would be great if he was!
God bless.