1. Sheethal is Shyam's sister. He came to know that ASR has broke away from his sister and wanted to take revenge, that is why he married his sister Anjali. If he truely loves Anjali he will never do all this to her.
2. After all his plans fail to bring down ASR. Sister comes into play, both are taking revenge.
At least one loop hole will be closed with this storyline-What made Shyam marry Anjali if he did not love her, only for money?