Unfortunately or fortunately, Siddharth happened to overhear the part of the conversation, not really a conversation but anyways, he overheard his bhaiyya dictating the law! 

He technically overheard it, but he is officially still unaware of it. Before the law became official and his hands are tied, he felt like he should talk to Devansh. The boy has crossed too many red lines, and Siddharth hoped that the boy realized what he did. He felt the need to prepare the boy, so that the things don't escalate more than what they are already. He never had any first hand experience of his bhaiyya's anger, but he definitely did watch his other brothers being at the end of such anger. And that was more than enough motivation for him to toe all the lines. But Devansh didn't even have second hand experience like he did. With these thoughts in mind, he entered Devansh's room, only to find him staring the family wall, while Anirudh settled on a couch to a side, doing nothing.