Oh Divya! I think you missed it. Please listen again what he said at 13 mins 47 sec. He said"... Natasha! woh jaha tak mujhe pata hain, woh AK ki ho hi nahi sakti..."It menas he is claiming without having enough of the proofs.
Well I missed it. So happy that without knowing anything he is feeling that Natasha is not AK's daughter. That takes him to the truth which he deserves to know.
We have to admitt one thing that according to him Natasha is still AK's daughter. May be he said those words out of anger or possessiveness towards Tanuja. But he said those so he is feeling something towards Natasha. Thats indeed Silver Lining in Dark Cloud.