Yes, it doesn't seem like anyone knows of the house other than Vani and Vijay - I'm guessing it must be Vani's maternal estate or something like that which she didn't reveal to Kuldeep (knowing his true nature) and then she passed that on to Vijay. There is no way Kuldeep knows of that house - though i'm not sure why they show flashbacks of Vani's abusive past when she sees that house - I don't think they have lived there.
I also hope she gets back her memory and Vijay and her probably with Vedika and Vandu in the loop expose Kuldeep.
I don't understand though why Vedika knowing it all doesn't sit down with Kunal and tell him everything? Right from how she has witnessed their mother being abused at the hands of their father to - basically what she told Vandu. Kunal might not believe her - but she has nothing to lose - she also knows he was up to stopping the wedding etc. Kunal does trust his sister so what she says will definitely at least get him thinking.
Hope he gets more adult like soon!