I'm not sure specifically as I haven't come across this 'kya dill mein hai' story in detail. It could be about a person's inner journey and the final realization or outcome in their heart.
The movie 'Ek Banda Kafi Hai' does have roots in reality. It takes elements from actual stories and weaves them into a compelling narrative. However, there might be some artistic liberties taken to make it more engaging for the audience.
Family and society could be important themes as well. In many Urdu novels, the family and the social environment play a huge role in shaping the characters' lives and their relationships. So in 'ek sitam aur meri jaan urdu novel', the family might be either a support or a hindrance in the story, and society's norms could be a factor in the'sitam' or the pain.
Well, without having read it in detail, it could be the unique way it portrays relationships. The title itself 'ek bar kaho tum meri ho' gives an impression of longing and a deep emotional connection, which might be explored in a special way in the novel.
I don't have definite information. It could be a mix of real and fictional elements. Maybe check reviews or interviews related to it to get a clearer picture.