i think she killled Kabir b/c of the money and Appa b/c she knew that she was the killer and that Appa didnt leave her any money.
these are all cluse that point to Nadira
i dont think it was Azaan b/c he loved Kabir alot and i dont its the dad b/c he loves his kid and how could Zareen do it b/c she loved Kabir the most and if she wanted she could have killed him when he was a baby