The reason forNivis divorce with anupam not shown.Anupam loved sneha very much
.in couple of instances he was shown taking care of sneha in prernas absence.at one point he complained even that moloy not giving a chance to play with sneha.
I guess post komolika went to orphanage and gave the kid Anurag secretively took sneha and gave it to anupam.
The only person to know abt this whole drama should be Anupam.If Bajaj had kept sneha secretively somewhere then that would go against him