False Dowry/Money Allegations and Custody issues

My brother and his wife have a son. (Telangana). Their marriage had no dowry involved. She has now taken the son to her native place (Uttar Pradesh), while my brother was in the US. Turns out she cheated on my brother, but her family are denying any allegations. She also used to beat her son and used to threaten him that she would push him off the balcony if he didn't behave. My brother found out that she cheated on him while he was in the US and the verbal abuses started towards my parents. My parents love their grandson and only want the grandson to be reunited with the father. The grandson is just 3 years old and will turn 4 this year. But they were abused horribly when they went to meet him 2 months ago. So, this is even more difficult. Most abuses were verbal and we couldn't record anything. She also said that she would kill my entire family. My brother has returned from the US but could got not go to UP because of the lockdown. Now I have a text message from her with the worst expletives used and all kinds of false allegations about how we took money from her, which we never did and how my the ladies in my family are whores. And now, she has started calling our relatives telling them how my family is a bunch of whores (Many more hindi expletives used) and how we asked for money. A part of the message to me was: क्या हुआ अभी चुप क्यों हो गई हरामजादी मुझे पता है किस हरामजादी की वजह से बोल नहीं पा रही है आखिर एक है रंडी तो है नहीं घर में।एक रंडी ने रंडी को है पैदा किया है पूरा घर है हरामियों से भरा पड़ा है। How do I protect my family from this person? How do we get the custody of my brother's son with him because this woman is not fit to be a mother to him? How do we ensure the divorce happens but without any alimony because of the threats we received from her and her abuses?