If Kaku breaks down after knowing Karishma's miscarriage and keep chanting no chiraag, Vinu died etc., Virat might blurt out the truth about Vinayak is the real Vinu, his and Sai ka ansh to whom Pakhi gave birth. Knowing this Kaku yo stop Sai from taking their vansh ka ansh away might make samjotha and accept Sai to live with them in CN but not to reveal the truth to the external world as her political career will be at stake.
This might provoke Pakhi to take the drastic step and run away with Vinu and also the family fortune as she is running the business.
