So there is history and its passed on. I can see why Arnav wasn't told about it worried that he might repeat what his mother did. But in the way Arnav spoke, it looks like his mother's case was extreme compared to his. I do not condone the family to get him married as he, like any other person out there deserves equal opportunity but the family have hidden too many things from Khushi. Khushi's perspective on everything that's been going on has been influenced by the half information provided to her - as Arnav points that out. Its just got messy because everyone wants to protect everyone else and in the process hurting the very person they were out to protect. Khushi and grandma have unwittingly hurt Arnav. He is right - it wasn't a news that once could hide but may be they were scared Khushi's life was in danger. What's the guarantee its not endangered when she wasn't pregnant? He hurt himself - which I am unable to decipher was a result of psychosis or a conscious action. On the day of party he does say that "everything will be okay" so unless he is shifting with dis-associative personality disorder or just is making this all up, it very much sounds like a segue into something more dangerous.