1) Khushi and Arnav get caught in some compromising situation. Buaji etc get pissed and say she was about to get married and Arnav has ruined her chances, so he gets married to her. Later he finds out about Shyam and thinks Khushi is home wrecker and gets even more angry.
2) Khushi comes to tell Raizadas that she is getting married because she has no choice. Her father wants her married. Arnav overhears and can't help himself… tells her he will marry her and bail her family out and that in some months they must divorce. Later he finds out about Shyam and thinks Khushi is home wrecker and decides to stay married so that Shyam can't have her
3) Arnav finds out that Khushi is getting married. He rushes over to tell her he loves her, then finds out she is marrying Shyam. Thinks she is out to ruin his sister's life and abducts her and forcefully marries her thinking she is home wrecker and needs to be taught a lesson
My bet is on the third one.
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