I know that we had this topic before. I was watching SP in the US yesterday and the Brijesh completely changed his converstation with Saloni after he saw Urvashi coming.
He wants the child. I think that he might have even married Urvashi in front of a fake pandit to make her happy so can't later claim to be his wife in any possible way.
I think that he is testing how far Urvashi is willing to go to mistreat her own sister (which we know that she is not, but he doesn't).
And maybe he wants to teach Tara a lesson also. Tara is the one that started all this.