I was thinking, how will Kunal change? I think that the first step might come when Nimmo reveals how Nikita really is. Kunal will probably be kinda mad that his sis acts the way she does (double standard but which bro would be okay with it?) and in her defense she'll say that he's the same way. Maybe that might get him to initially see the light...
...Other than that, Nimmo's disapproval of his lifestyle when he starts to like her will get him to change of course...
Kajal