After divorce by 13b child custody

As per HMA I have been paid maintenance of Rs 5000 PM as decided by Session court. To increase the maintenance opponent went to high court where court has asked for mutual divorce under 13b after payment of Rs 8.5 L + 0.60L[as arrears of maintenance]. I have almost 9 years of marriage life when she left my home with my 9 months old son[DoB Sept 2012]. I have my elder daughter [DoB feb-2006]. It has been ordered that child Custody would be as it was but brother and sister allow to meet. Now we have been divorced u/s 13b. She has Re-married. They don't allow my daughter to meet my son. It is still pending to confirm divorce after 6 month but divorced by stamp paper. So my question is now custody of my six years old son is possible by law? My son is living with her parents at present and she went alone present where she Re-married. Can I object the same when I will go to court after 6 month to finish formalities of 13B. Can she kept my son custody even if Re-married. Can we challenge this