Anu, just google it under google news.. there are soo many articles about this. There was even an article about Robert having "necked" the actress from inception, Talulah Riley.
I suppose it thier personal life but if both them are serious then they should let it out in the open now. What is the point trying to hide something which isn't a secret. Plus Kristen doesn't seem to be too keen on the fame from Hollywood and wants to return to theatre with RP. They are both so connected that I don't know how they can just be nothing besides a couple!