My theory
Abhinav has kept some notes for abhir in chutkula diary. That he always felt he never belonged with akshara. He never had that chemistry with her like how abhi has. He felt he is the unwanted guest who entered their life and now both Don't want to accept each other because of him. If something happens to it's abhir's responsibility to unite abhira. Kuch kuch hotha hai sasta track 
Ranij mukherji is abhinav here.
Kajor and srk are abhimanyu and akshara.
Even though srk and rani did lead a happy life rani always felt she replaced some one.
Abhinav will feel the same and hence abhir is behind abhira to get them married 😄
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